# Endangered and Threatened Wildlife and Plants; Endangered Species Status for Chamaecrista lineata var. keyensis (Big Pine Partridge Pea), Chamaesyce deltoidea ssp. serpyllum (Wedge Spurge), and Linum arenicola (Sand Flax), and Threatened Species Status for Argythamnia blodgettii (Blodgett's Silverbush)

> Briefs, arguments, decisions, and more.

URL: https://www.frixlaw.com/law-library/documents/fr%3A2015-24291

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** September 29, 2015
- **Citation:** 80 FR 58536

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R4-ES-2015-0137]; [4500030113]
RIN 1018-AZ95
Endangered and Threatened Wildlife and Plants; Endangered Species Status for Chamaecrista lineata var. keyensis (Big Pine Partridge Pea), Chamaesyce deltoidea ssp. serpyllum (Wedge Spurge), and Linum arenicola (Sand Flax), and Threatened Species Status for Argythamnia blodgettii (Blodgett's Silverbush)

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service or USFWS), propose to list four plants from south Florida under the Endangered Species Act of 1973, as amended (Act):
Chamaecrista lineata
var.
keyensis
(Big Pine partridge pea),
Chamaesyce deltoidea
ssp.
serpyllum
(wedge spurge), and
Linum arenicola
(sand flax) as endangered species, and
Argythamnia blodgettii
(Blodgett's silverbush) as a threatened species. If we finalize this rule as proposed, it would extend the Act's protections to these plants.

DATES:

We will accept comments received or postmarked on or before November 30, 2015. Comments submitted electronically using the Federal eRulemaking Portal (see
ADDRESSES
, below) must be received by 11:59 p.m. Eastern Time on the closing date. We must receive requests for public hearings, in writing, at the address shown in
FOR FURTHER INFORMATION CONTACT
by November 13, 2015.

ADDRESSES:

You may submit comments by one of the following methods:

(1)
Electronically:
Go to the Federal eRulemaking Portal:
http://www.regulations.gov.
In the Search box, enter FWS-R4-ES-2015-0137, which is the docket number for this rulemaking. Then, in the Search panel on the left side of the screen, under the Document Type heading, click on the Proposed Rules link to locate this document. You may submit a comment by clicking on “Comment Now!”

(2)
By hard copy:
Submit by U.S. mail or hand-delivery to: Public Comments Processing, Attn: FWS-R4-ES-2015-0137; U.S. Fish and Wildlife Service, MS: BPHC, 5275 Leesburg Pike, Falls Church, VA 22041-3803.

We request that you send comments only by the methods described above. We will post all comments on
http://www.regulations.gov.
This generally means that we will post any personal information you provide us (see
Public Comments,
below, for more information).

FOR FURTHER INFORMATION CONTACT:

Larry Williams, State Supervisor, U.S. Fish and Wildlife Service, South Florida Ecological Services Field Office, 1339 20th Street, Vero Beach, FL 32960; by telephone 772-562-3909; or by facsimile 772-562-4288. Persons who use a telecommunications device for the deaf (TDD) may call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Executive Summary

Why we need to publish a rule.
Under the Act, if we determine that a species is an endangered or threatened species throughout all or a significant portion of its range, we must publish a proposed rule to list the species in the
Federal Register
and make a determination on our proposal within 1 year. Listing a species as an endangered or threatened species can only be completed by issuing a rule.

This rule
proposes the listing of
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum,
and
Linum arenicola
as endangered species, and
Argythamnia blodgettii
as a threatened species. The four plants are candidate species for which we have on file sufficient information on biological vulnerability and threats to support preparation of a listing proposal, but for which development of a listing rule has until now been precluded by other higher priority listing activities. This rule reassesses all available information regarding status of and threats to the four plants.

The basis for our action.
Under the Act, we may determine that a species is an endangered or threatened species based on any of five factors: (A) The present or threatened destruction, modification, or curtailment of its habitat or range; (B) overutilization for commercial, recreational, scientific, or educational purposes; (C) disease or predation; (D) the inadequacy of existing regulatory mechanisms; or (E) other natural or manmade factors affecting its continued existence. We have determined that the threats to
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola,
and
Argythamnia blodgettii
consist primarily of habitat loss and modification through urban and agricultural development, and lack of adequate fire management (Factor A); and the proliferation of nonnative invasive plants, stochastic events (hurricanes and storm surge), maintenance practices used on roadsides and disturbed sites, and sea level rise (Factor E). Existing regulatory mechanisms have not been adequate to reduce or remove these threats (Factor D).

We will seek peer review.
We will seek comments from independent specialists to ensure that our determinations are based on scientifically sound data, assumptions, and analyses. We will invite these peer reviewers to comment on this listing proposal.

Information Requested

Public Comments

We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned governmental agencies, Native American tribes, the scientific community, industry, or any other interested parties concerning this proposed rule. We particularly seek comments concerning:

(1) The four plants' biology, range, and population trends, including:

(a) Biological or ecological requirements of these plants, including habitat requirements for establishment, growth, and reproduction;

(b) Genetics and taxonomy;

(c) Historical and current ranges, including distribution patterns;

(d) Historical and current population levels, and current and projected trends; and

(e) Past and ongoing conservation measures for the plants, their habitats, or both.

(2) Factors that may affect the continued existence of these plants, which may include habitat modification or destruction, overutilization, disease, predation, the inadequacy of existing regulatory mechanisms, or other natural or manmade factors.

(3) Biological, commercial trade, or other relevant data concerning any threats (or lack thereof) to these plants and existing regulations that may be addressing those threats.

(4) Current or planned activities in the areas occupied by these plants and possible impacts of these activities on these plants.

(5) Additional information concerning the biological or ecological requirements

of these plants, including pollination and pollinators.

(6) Scientific information or analysis informing whether these plants more closely meet the definition of endangered or of threatened under the Act.

Please include sufficient information with your submission (such as scientific journal articles or other publications) to allow us to verify any scientific or commercial information you include.

Please note that submissions merely stating support for or opposition to the action under consideration without providing supporting information, although noted, will not be considered in making a determination, as section 4(b)(1)(A) of the Act (16 U.S.C. 1531
et seq.
) directs that determinations as to whether any species is an endangered or threatened species must be made “solely on the basis of the best scientific and commercial data available.”

You may submit your comments and materials concerning this proposed rule by one of the methods listed in the
ADDRESSES
section. We request that you send comments only by the methods described in the
ADDRESSES
section.

If you submit information via
http://www.regulations.gov,
your entire submission—including any personal identifying information—will be posted on the Web site. If your submission is made via a hardcopy that includes personal identifying information, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so. We will post all hardcopy submissions on
http://www.regulations.gov.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on
http://www.regulations.gov,
or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, South Florida Ecological Services Field Office (see
FOR FURTHER INFORMATION CONTACT
).

Public Hearing

Section 4(b)(5) of the Act provides for one or more public hearings on this proposal, if requested. Requests must be received within 45 days after the date of publication of this proposed rule in the
Federal Register
. Such requests must be sent to the address shown in the
FOR FURTHER INFORMATION CONTACT
section. We will schedule public hearings on this proposal, if any are requested, and announce the dates, times, and places of those hearings, as well as how to obtain reasonable accommodations, in the
Federal Register
and local newspapers at least 15 days before the hearing.

Peer Review

In accordance with our joint policy on peer review published in the
Federal Register
on July 1, 1994 (59 FR 34270), we will seek the expert opinions of at least three appropriate and independent specialists regarding this proposed rule. The purpose of peer review is to ensure that our listing determinations are based on scientifically sound data, assumptions, and analyses. The peer reviewers have expertise in the biology, habitat, and conservation status of these plants, which will inform our determinations. We invite comment from the peer reviewers during the public comment period.

Previous Federal Actions

On January 9, 1975, as directed by the Act, the Secretary for the Smithsonian Institution submitted a report to Congress on potential endangered and threatened plant species of the United States (Smithsonian 1975, entire). The report identified more than 3,000 plant species as potentially either endangered or threatened, including
Argythamnia blodgettii, Chamaecrista lineata
var.
keyensis
(under the former name
Cassia keyensis
),
Chamaesyce deltoidea
ssp.
serpyllum
(under the name
Chamaesyce
(
Euphorbia
)
deltoidea
ssp.
serpyllum
), and
Linum arenicola
(Smithsonian 1975, pp. 56, 58, 61, 81). On July 1, 1975, we published in the
Federal Register
(40 FR 27824) our notification that we considered this report to be a petition to list the identified plants as either endangered or threatened under the Act. The 1975 notice solicited information from Federal and State agencies, and the public, on the status of the species.

On December 15, 1980, we published in the
Federal Register
(45 FR 82480) our notice of review of plant taxa for listing as endangered or threatened species. In that document,
Argythamnia blodgettii, Chamaecrista lineata
var.
keyensis
(under the former name
Cassia keyensis
),
Chamaesyce deltoidea
ssp.
serpyllum
(under the former name
Euphorbia deltoidea
ssp.
serpyllum
), and
Linum arenicola
were identified as Category 1 species (taxa for which we had enough biological information to support listing as either endangered or threatened). As a result, we considered all four plants to be candidates for addition to the Federal List of Endangered and Threatened Plants. The 1980 notice solicited information from Federal and State agencies, and the public, on the status of the four plant species.

On November 28, 1983, we published a document in the
Federal Register
(48 FR 53640) assigning a listing priority number (LPN) to two of the four plant species in accordance with our Listing Priority Guidance (48 FR 43098; September 21, 1983).
Argythamnia blodgettii
and
Linum arenicola
were assigned an LPN of 2, which meant that information that the Service possessed indicated that proposing to list as endangered or threatened was possibly appropriate but we lacked substantial information on biological vulnerability and threat(s) to support a proposed listing.

On September 27, 1985, we published a document in the
Federal Register
(50 FR 39526) assigning LPNs to all four of the plant species in accordance with our Listing Priority Guidance (48 FR 43098; September 21, 1983).
Argythamnia blodgettii
and
Linum arenicola
both retained an LPN of 2, which meant that information that the Service possessed indicated that proposing to list as endangered or threatened was possibly appropriate but we lacked substantial information on biological vulnerability and threat(s) to support a proposed listing.
Chamaecrista lineata
var.
keyensis
(under the former name
Cassia keyensis
) and
Chamaesyce deltoidea
ssp.
serpyllum
(under the former name
Euphorbia deltoidea
ssp.
serpyllum
) were both assigned an LPN of 1, which meant the Service had on file substantial information on biological vulnerability and threat(s) to support the appropriateness of proposing to list as endangered or threatened. We recognized at that time that any proposed listing action may take “some years” because of the “large number of taxa” at issue.

The 1990 candidate notice of review (CNOR) published in the
Federal Register
on February 21, 1990 (55 FR 6184). In that CNOR,
Argythamnia blodgettii
and
Linum arenicola
both retained an LPN of 2, and
Chamaecrista lineata
var.
keyensis
and
Chamaesyce deltoidea
ssp.
serpyllum
both retained an LPN of 1. Candidate species are assigned LPNs based on immediacy and magnitude of threats, as well as taxonomic status. The lower the LPN, the higher priority that species is for us to determine appropriate action using our available resources. We determined at that time that proposing to list was warranted, but was precluded due to workloads and priorities.

All four plants remained on the candidate list in the 1993 CNOR (58 FR 51144; September 30, 1993), with
Argythamnia blodgettii
and
Linum arenicola
both retaining an LPN of 2, and
Chamaecrista lineata
var.
keyensis

and
Chamaesyce deltoidea
ssp.
serpyllum
being assigned an LPN of 3C (taxa that have proven to be more abundant or widespread than previously believed and/or those that are not subject to any identifiable threat).

The 1999 CNOR (64 FR 57534; October 25, 1999) retained
Chamaecrista lineata
var.
keyensis
and
Chamaesyce deltoidea
ssp.
serpyllum
as candidates and assigned an LPN of 6 to both, retained
Linum arenicola
as a candidate and assigned an LPN of 2, and retained
Argythamnia blodgettii
as a candidate and assigned an LPN of 11.

Chamaecrista lineata
var.
keyensis
and
Chamaesyce deltoidea
ssp.
serpyllum
remained on the candidate list from 2001 to 2006, with the LPN of 6 (66 FR 54808, October 30, 2001; 67 FR 40657, June 13, 2002; 69 FR 24876, May 4, 2004; 70 FR 24870, May 11, 2005; 71 FR 53756, September 12, 2006). In the December 6, 2007, CNOR (72 FR 69034), we changed the LPN of
Chamaecrista lineata
var.
keyensis
and
Chamaesyce deltoidea
ssp.
serpyllum
from a 6 to a 9 because the threats to the species were found to be of lower magnitude than previously known.
Chamaecrista lineata
var.
keyensis
and
Chamaesyce deltoidea
ssp.
serpyllum
remained on the candidate list as published in the CNORs from 2008 to 2014 with the LPN of 9 (73 FR 75176, December 10, 2008; 74 FR 57804, November 9, 2009; 75 FR 69222, November 10, 2010; 76 FR 66370, October 26, 2011; 77 FR 69994, November 21, 2012; 78 FR 70104, November 22, 2013; 79 FR 72450, December 5, 2014).

Linum arenicola
remained on the candidate list from 2001 to 2009, with the LPN of 2 (66 FR 54808, October 30, 2001; 67 FR 40657, June 13, 2002; 69 FR 24876, May 4, 2004; 70 FR 24870, May 11, 2005; 71 FR 53756, September 12, 2006; 72 FR 69034, December 6, 2007; 73 FR 75176, December 10, 2008; 74 FR 57804, November 9, 2009). In the November 10, 2010, CNOR (75 FR 69222), we changed the LPN of
L. arenicola
from a 2 to a 5 because of the threats to the species were found to be of lower magnitude than previously known and new data showing a larger population.
L. arenicola
remained on the candidate list as published in the CNORs from 2011 to 2014 with the LPN of 5 (76 FR 66370, October 26, 2011; 77 FR 69994, November 21, 2012; 78 FR 70104, November 22, 2013; 79 FR 72450, December 5, 2014).

Argythamnia blodgettii
remained on the candidate list from 2001 to 2014, with the LPN of 11 (66 FR 54808, October 30, 2001; 67 FR 40657, June 13, 2002; 69 FR 24876, May 4, 2004; 70 FR 24870, May 11, 2005; 71 FR 53756; September 12, 2006; 72 FR 69034, December 6, 2007; 73 FR 75176, December 10, 2008; 74 FR 57804, November 9, 2009; 75 FR 69222, November 10, 2010; 76 FR 66370, October 26, 2011; 77 FR 69994, November 21, 2012; 78 FR 70104, November 22, 2013; 79 FR 72450, December 5, 2014).

For all four of the plant species, the 2005 CNOR (70 FR 24870; May 11, 2005) included a “warranted but precluded” finding in response to a May 11, 2004, petition to list the species.

On May 10, 2011, as part of a settlement agreement with a plaintiff, the Service filed a proposed work plan with the U.S. District Court for the District of Columbia. The work plan would enable the agency to, over a period of 6 years, systematically review and address the needs of more than 250 species listed within the 2010 CNOR, including
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola,
and
Argythamnia blodgettii,
to determine if these species should be added to the Federal Lists of Endangered and Threatened Wildlife and Plants. This work plan would enable the Service to again prioritize its workload based on the needs of candidate species, while also providing State wildlife agencies, stakeholders, and other partners clarity and certainty about when listing determinations will be made. On July 12, 2011, the Service reached an agreement with another plaintiff group and further strengthened the work plan, which would allow the agency to focus its resources on the species most in need of protection under the Act. These agreements were approved by the court on September 9, 2011. The four species are proposed for listing pursuant to these agreements.

Background

It is our intent to discuss below only those topics directly relevant to the listing of
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum,
and
Linum arenicola
as endangered, and
Argythamnia blodgettii
as threatened, in this proposed rule.

Chamaecrista lineata
var.
keyensis
(Big Pine partridge pea)

Species Description

Chamaecrista lineata
var.
keyensis
is a small, prostrate to ascending, perennial, herbaceous shrub that is 10-80 centimeters (cm) (3.9-31.5 inches (in)) tall, with yellow flowers and pinnately compound leaves (each leaf consists of a main stem with multiple leaflets lined up along on each side). It has one to several branched stems arising from a contorted rootstock. New branches are covered in soft, fuzzy hairs. The leaves are 1.7-4.0 cm (0.7-1.6 in) long, with 5 to 9 pairs of leaflets. Flowers consist of five sepals 9-20 mm (0.4-0.8 in) long that are fused together near their bases; five yellow petals 11-15 mm (0.4-0.6 in) long, with one slightly larger than the others; 10 reddish-purple stamens; and a single, elongate style. The fruit is an elongate pod, roughly similar to that of a pea, 33-45 mm (1.3-1.8 in) long and 4.5-5.0 mm (0.19-0.17 in) wide, with a soft fuzzy texture, which turns gray with age and eventually split open to release seeds (Irwin and Barneby 1982, p. 757; Small 1933, pp. 662-663).

Taxonomy

John Loomis Blodgett was the first to collect
Chamaecrista lineata
var.
keyensis,
sometime between 1838 and 1852, on Big Pine Key (Bradley and Gann 1999, p. 17). Pollard (1894, p. 217) assigned the plants on Big Pine Key to the existing taxon
Cassia grammica.
John K. Small (1903, p. 587; 1913, p. 58) followed this usage, but used the genus
Chamaecrista
(considered a subgenus within
Cassia
or a genus unto itself variously by many authors). In 1917, Pennell (p. 344) recognized the Big Pine Key plant as a distinct endemic species, naming it
Chamaecrista keyensis.
This name was retained by Small (1933, p. 663) in his Manual of the Southeastern Flora. In an exhaustive study of
Cassia
and
Chamaecrista,
Irwin and Barneby (1982, p. 757) assigned plants in Florida and parts of the West Indies to the existing taxon
Chamaecrista lineata,
and assigned the Big Pine Key plants to var.
keyensis,
retaining them as endemic to the Florida Keys. Isely (1990, p. 33), Wunderlin (1998, p. 348), and Wunderlin and Hansen (2003, p. 441) have followed this treatment. The online Atlas of Florida Vascular Plants (Wunderlin and Hansen 2014, p. 1) uses
Chamaecrista lineata
var.
keyensis.
The Integrated Taxonomic Information System (2015, p. 1) uses the name
Chamaecrista lineata
var.
keyensis
and indicates that this taxonomy is accepted. Based upon the best available scientific information,
Chamaecrista lineata
var.
keyensis
is a distinct taxon, endemic to the lower Keys in Monroe County, Florida. Synonyms are
Cassia keyensis
(Pennell) J.F. Macbr and
Chamaecrista keyensis
Pennell.
Chamaecrista lineata
var.
keyensis
is related to, and superficially resembles,
Chamaecrista fasciculata,
the partridge pea, a common species which occurs throughout Florida.

Climate

The climate of south Florida where
Chamaecrista lineata
var.
keyensis
occurs is classified as tropical savanna and is characterized by distinct wet and dry seasons and a monthly mean temperature above 18 degrees Celsius (°C) (64.4 degrees Fahrenheit (°F)) in every month of the year (Gabler
et al.
1994, p. 211). Freezes can occur in the winter months, but are rare at this latitude in south Florida. Rainfall in the lower Keys, where
C. lineata
var.
keyensis
occurs exclusively, varies from an annual average of 89-102 cm (35-40 in). Approximately 75 percent of yearly rainfall occurs during the wet season from June through September (Snyder
et al.
1990, p. 238).

Habitat

Chamaecrista lineata
var.
keyensis
occurs in pine rocklands of the lower Florida Keys, and adjacent disturbed sites, including roadsides.

Pine Rocklands:
Pine rocklands are a unique and highly imperiled ecosystem found on limestone substrates in south Florida and a few islands in the Bahamas. In Florida, pine rocklands are located on the Miami Rock Ridge in present day Miami and in Everglades National Park, in the Florida Keys, and in the Big Cypress Swamp. While all four plants in this proposed rule occur primarily in pine rocklands, they have not been recorded in the Big Cypress Swamp area. Pine rocklands differ to some degree between and within these areas with regard to substrate (
e.g.,
amount of exposed limestone, type of soil), elevation, hydrology, and species composition (both plant and animal).

Pine rocklands occur in a mosaic with primarily two other natural community types—rockland hammock and marl prairie. Pine rocklands grade into rockland hammock; pine rocklands have an open pine canopy, and rockland hammock has a closed, hardwood canopy. Marl prairies differ from pine rocklands in having no pines, an understory dominated by grasses and sedges, and a minimal cover of shrubs (FNAI 2010, p. 63).

The total remaining acreage of pine rocklands in Miami-Dade and Monroe Counties is now 8,981 hectares (ha) (22,079 acres (ac)) (approximately 8,140 ha (20,100 ac)) in Miami-Dade County, and 801 ha (1,979 ac) in the Florida Keys (Monroe County).

Pine rocklands are characterized by an open canopy of
Pinus elliottii
var.
densa
(South Florida slash pine) with a patchy understory of tropical and temperate shrubs and palms and a rich herbaceous layer of mostly perennial species, including numerous species endemic to South Florida. Outcrops of weathered oolitic (small, rounded particles or grains) limestone are common, and solution holes may be present. This subtropical, pyrogenic flatland can be mesic or xeric depending on landscape position and associated natural communities (FNAI 2010a, p. 1).

Pine rocklands occur on relatively flat, moderately to well-drained terrain from 2-7 meters (m) (6.5 to 23 feet (ft)) above sea level (FNAI 2010a, p. 2). The oolitic limestone is at or very near the surface, and there is very little soil development. Soils are generally composed of small accumulations of nutrient-poor sand, marl, clayey loam, and organic debris in depressions and crevices in the rock surface. Organic acids occasionally dissolve the surface limestone causing collapsed depressions in the surface rock called solution holes (FNAI 2010a, p. 1). Drainage varies according to the porosity of the limestone substrate, but is generally rapid. Consequently, most sites are wet for only short periods following heavy rains. During the rainy season, however, some sites may be shallowly inundated by slow-flowing surface water for up to 60 days each year (FNAI 2010a, p. 1).

Pine rocklands have an open canopy of South Florida slash pine, generally with multiple age classes. The diverse, open shrub and subcanopy layer is composed of more than 100 species of palms and hardwoods (FNAI 2010a, p. 1), most derived from the tropical flora of the West Indies (FNAI 2010a, p. 1). Many of these species vary in height depending on fire frequency, getting taller with time since fire. These may include
Serenoa repens
(saw palmetto),
Sabal palmetto
(cabbage palm),
Coccothrinax argentata
(silver palm),
Thrinax morrisii
(Key thatch palm),
Myrica cerifera
(wax myrtle),
Rapanea punctata
(myrsine),
Metopium toxiferum
(poisonwood),
Byrsonima lucida
(locustberry),
Dodonaea viscosa
(varnishleaf),
Tetrazygia bicolor
(tetrazygia),
Guettarda scabra
(rough velvetseed),
Ardisia escallonioides
(marlberry),
Psidium longipes
(longstalked stopper),
Sideroxylon salicifolium
(willow bustic), and
Rhus copallinum
(winged sumac). Short-statured shrubs may include
Quercus elliottii
(running oak),
Randia aculeata
(white indigoberry),
Crossopetalum ilicifolium
(Christmas berry),
Morinda royoc
(redgal), and
Chiococca alba
(snowberry).

Grasses, forbs, and ferns make up a diverse herbaceous layer ranging from mostly continuous in areas with more soil development and little exposed rock to sparse where more extensive outcroppings of rock occur. Typical herbaceous species may include
Andropogon
spp.;
Schizachyrium gracile, S. rhizomatum,
and
S. sanguineum
(bluestem grasses);
Aristida purpurascens
(arrowleaf threeawn);
Sorghastrum secundum
(lopsided indiangrass);
Muhlenbergia capillaris
(hairawn muhly);
Rhynchospora floridensis
(Florida white-top sedge);
Tragia saxicola
(pineland noseburn);
Echites umbellata
(devil's potato);
Croton linearis
(pineland croton); several species of
Chamaesyce
spp. (sandmats);
Chamaecrista fasciculata
(partridge pea);
Zamia pumila
(coontie);
Anemia adiantifolia
(maidenhair pineland fern);
Pteris bahamensis
(Bahama brake); and
Pteridium aquilinum
var.
caudatum
(lacy bracken) (FNAI 2010a, p. 1).

There are noticeable differences in species composition between the pine rocklands found in the Florida Keys and the mainland. The shrub layer in pine rocklands occurring in the northern end of the Miami Rock Ridge more closely resembles pine flatwoods as a result of the amount of sandy soils in this area, with species such as
Lyonia fruticosa
(staggerbush),
Quercus minima
(dwarf live oak),
Quercus pumila
(running oak), and
Vaccinium myrsinites
(shiny blueberry) becoming more common (Snyder
et al.
1990, p. 255). Pine rocklands in the lower Florida Keys have a subcanopy composed of several palms such as
Thrinax morrisii, Thrinax radiata
(Florida thatch palm), and
Coccothrinax argentata,
and hardwoods such as
Byrsonima lucida
and
Psidium longipes
(Bradley 2006, p. 3). The diversity of the herbaceous layer decreases as the density of the shrub layer increases (
i.e.,
as understory openness decreases), and pine rocklands on the mainland have a more diverse herbaceous layer due to the presence of temperate species and some tropical species that do not occur in the Florida Keys (FNAI 2010, p. 63).

Pine rocklands are maintained by regular fire, and are susceptible to other natural disturbances such as hurricanes, frost events, and sea level rise (SLR) (Ross
et al.
1994). Fires historically burned on an interval of approximately every 3 to 7 years, and were typically started by lightning strikes during the frequent summer thunderstorms (FNAI 2010a, p. 3). Mature South Florida slash pine is highly fire-resistant (Snyder
et al.
1990, p. 259). Above-ground portions of hardwood shrubs are typically killed by fire, but often resprout below ground; palms typically produce new growth post-fire from their unaffected apical buds. The amount of woody understory growth is directly related to the length

of time since the last fire. Herbaceous diversity declines with time since last fire. The ecotone between pine rocklands and rockland hammock is abrupt when regular fire is present in the system. However, when fire is removed, the ecotone becomes more gradual and subtle as hardwoods encroach into the pineland (FNAI 2010a, p. 3). If fire is excluded for 20 to 30 years, hardwoods will come to dominate the community and hammock conditions will prevail, which further discourage fires from spreading except in drought conditions. Presently, prescribed fire must be periodically introduced into pine rocklands to sustain community structure, prevent invasion by woody species, maintain high herbaceous diversity (Loope and Dunevitz 1981, pp. 5-6; FNAI 2010a, p. 3), and prevent succession to rockland hammock.

Pine rocklands are also susceptible to natural disturbances such as hurricanes and other severe storms, during which trees may be killed, thereby helping to maintain the open canopy that is essential to pine rocklands plants. During such events, pine rocklands near the coast may be temporarily inundated by saltwater, which can also kill or damage vegetation (Snyder
et al.
1990, p. 251). These sporadic but potentially major disturbances, along with burning, create the dynamic nature of the pine rocklands habitat. Some currently unsuitable areas may become open in the future, while areas currently open may develop more dense canopy over time, eventually rendering that portion of the pine rocklands unsuitable for pine rocklands endemic plants.

Within pine rocklands habitat,
Chamaecrista lineata
var.
keyensis
is associated with areas that have few hardwoods and overstory palms are abundant (Bradley and Gann 1999, p 17-18).
C. lineata
var.
keyensis
plants are often in a clumped distribution surrounded by large areas of bare, open rock that do not support plant growth (Bradley 2006, p. 3).
C. lineata
var.
keyensis
is widespread in pine rocklands of Big Pine Key, but more frequent in the northern part of the island (Bradley 2006, p. 13). It is also more frequent in the interior of pine rocklands than on coastal edges (Bradley 2006, p. 13; Bradley and Saha 2009, p. 9).
C. lineata
var.
keyensis
is more abundant in areas with relatively higher elevation (Bradley and Saha 2009, p. 26), low shrub density, and a diverse herb layer (Bradley 2006, p. 37).

Roadsides:
Roadsides are a potentially important habitat for
Chamaecrista lineata
var.
keyensis
(Bradley 2006, p. 21). Where pine rocklands endemics such as
C. lineata
var.
keyensis
are found on road shoulders, the ground cover is dominated mostly by native herbs and grasses, and exotic lawn grasses have not been planted. Maintaining the roadsides in this condition through regular mowing, without planting sod, should continue to provide suitable habitat for
C. lineata
var.
keyensis
(Bradley 2006, p. 37).

Historical Range

Chamaecrista lineata
var.
keyensis
is endemic to the lower Florida Keys in Monroe County, Florida. Historical records exist for occurrences on five islands: Big Pine Key, No Name Key, Ramrod Key, Cudjoe Key, and Sugarloaf Key (Hodges and Bradley 2006, pp. 20-21).

Current Range, Population Estimates, and Status

The current range of
Chamaecrista lineata
var.
keyensis
is Big Pine Key and Cudjoe Key. In 2007, Bradley and Saha (2009, pp. 9-11) surveyed Big Pine Key, Cudjoe Key, Little Pine Key, No Name Key, and Sugarloaf Key (the five islands in the Florida Keys containing pine rocklands) and observed
C. lineata
var.
keyensis
only on Big Pine Key and Cudjoe Key. It has not been reported from other islands for some time (Ramrod Key in 1911, No Name Key in 1916 (Hodges and Bradley 2006, p. 45), and Lower Sugarloaf Key in 2005 (Hodges and Bradley 2006, p. 21)). Accordingly,
C. lineata
var.
keyensis
is considered extirpated from Ramrod Key, No Name Key, and Lower Sugarloaf Key—3 of 5 (60 percent) of the islands where it was historically recorded (Bradley and Gann 1999, p. 18; Hodges and Bradley 2006, p. 21). Big Pine Key, Cudjoe Key, Little Pine Key, No Name Key, and Sugarloaf Key presently contain pine rocklands habitat. No pine rocklands currently exist on Ramrod Key.

Population data for
Chamaecrista lineata
var.
keyensis
have been collected periodically on Big Pine Key since 1955. Because of the size of Big Pine Key, sample study plots were used, as opposed to a complete search of all potential habitat. Multiple indicators show that the population on Big Pine Key has declined over the past 60 years (Bradley 2006, p. 35). Dickson (1955) and Alexander and Dickson (1972) reported densities of
C. lineata
var.
keyensis
from plots they established on Big Pine Key in 1951 and 1969, respectively. Dickson (1955) reports a mean density of 10,764 plants/ha (26,599 plants/ac). Alexander and Dickson (1972) report a mean density of 27,871 plants/ha (68,872 plants/ac). In 2005, Bradley (2006, p. 35) recorded 2,339 plants/ha (5,780 plants/ac), 23.4 percent and 9.0 percent of the 1955 and 1972 estimates, respectively. Hurricane Wilma, which passed over Big Pine Key on October 24, 2005, generated storm surge in the lower Keys of up to 10 feet (Bradley 2006, p. 11; Hodges 2010, p. 4). In 2007, density had dropped to 820 plant/ha (2,026 plants/ac) and had not fully rebounded after 9 years (Bradley
et al.
2015, pp. 21-22). By 2013, density had fallen to 657 plants/ha (1,624 plants/ac) (Bradley
et al.
2015, p. 21). In summary, the data from 2005 to 2013 demonstrate a 63.8 percent decline in the density of
C. lineata
var.
keyensis
on Big Pine Key (Bradley
et al.
2015, p. 48).

A second indicator, the frequency which
Chamaecrista lineata
var.
keyensis
occurred in sample plots on Big Pine Key from data collected in 2005, 2007, and 2013, also show a decline.
Chamaecrista lineata
var.
keyensis
was present in 37 percent of plots in 2005, and 19 percent of plots in 2013, respectively. This represents a 49 percent reduction in the species frequency in study plots (Bradley
et al.
2015, p. 48).

A third indicator, total population size for
Chamaecrista lineata
var.
keyensis
on publicly owned pine rocklands on Big Pine Key (478 ha (1,181 ac)), was estimated to be 866,659 plants in 2005 (pre-Hurricane Wilma), 391,944 in 2007 (2 years post-Wilma), and 313,914 in 2013 (8 years post-Wilma). This represents a population decrease of 64 percent (Bradley
et al.
2015, p. 21).

The most recent estimate (2013) of the
Chamaecrista lineata
var.
keyensis
population on Big Pine Key is 313,914 plants (Bradley
et al.
2015, p. 21). Since 82 percent of the pine rocklands on Big Pine Key are publicly owned, this estimate likely accounts for the majority of the population. The most recent estimate of the population on Cudjoe Key is 150 plants (Hodges and Bradley 2006, p. 21).

The decline in
Chamaecrista lineata
var.
keyensis
can be largely attributed to loss of pine rocklands habitat to development and modification of this habitat due to inadequate fire management. Folk (1991, p. 188) estimated that pine rocklands historically covered 1,049 ha (2,592 ac), about 44 percent of Big Pine Key. Pine rocklands now cover approximately 582 ha (1,438 ac) of Big Pine Key, 56 percent of the historical estimate by Folk (1991) (Bradley 2006, p. 4). Hurricanes and associated storm surge have also impacted population levels. These factors are discussed in detail below,

under Summary of Biological Status and Threats.

Table 1—Summary of the Status and Trends of the Known Occurrences of Chamaecrista lineata var. keyensis

Population
Ownership

Most recent
population estimate

Status
Trend

Big Pine Key

USFWS,
1
FWC
2
Monroe County, private

313, 914 (2014)
4

Extant
4

Declining.
4

Cudjoe Key

USFWS,
1
FWC
2

150 (2005)
3

Extant
3

Insufficient data.

Lower Sugar Loaf Key

USFWS,
1
FWC
2
, Monroe County

3 (2005)
3

Extirpated
3

No Name Key
unknown

no data (1916)
3

Extirpated
3

Ramrod Key
unknown

no data (1911)
3

Extirpated
3

1
U.S. Fish and Wildlife Service.

2
Florida Fish and Wildlife Conservation Commission.

3
Hodges and Bradley 2006, p. 45.

4
Bradley
et al.
2015, p. 21.

Biology

The reproductive biology and relationship to fire of
Chamaecrista lineata
var.
keyensis
has received a considerable amount of study. Significant findings are summarized below.

Life History and Reproduction: Chamaecrista lineata
var.
keyensis
is a perennial, but some stems will die back every year, and a small proportion of plants may go dormant for a year or more. Peak flowering and fruiting occurs in the summer from May to August, corresponding with increased rainfall during these months in the Florida Keys. Mature seedpods may contain 1 to 10 seeds. Seedlings may appear throughout the year, with a peak in the fall during September to October, immediately following seed dispersal. Seeds may persist in the soil seed bank for up to 3 years (Liu and Menges 2005, p. 1484).

Chamaecrista lineata
var.
keyensis
flowers require insect visitation for pollination. The anthers (pollen-bearing structures) have small pores from which pollen escapes when a visiting insect's wings vibrate the structure, a phenomenon known as buzz-pollination. Though many types of insects visit
C. lineata
var.
keyensis
flowers, effective pollination can be performed only by buzz-pollinating bees. Of the numerous bee species that visit the flowers, only
Xylocopa micans
and
Melissodes
spp. bees have been observed performing effective buzz-pollination (Liu and Koptur 2003, pp. 1184-1186).

Chamaecrista lineata
var.
keyensis
flowers are self-compatible (an individual can be fertilized with its own pollen), and seeds are generated both by self- and cross-pollination. However, seed set is higher when cross-pollination occurs. Seed germination rates are higher from cross-pollinated flowers, suggesting that inbreeding depression occurs in seeds produced through self-pollination (Liu and Koptur 2003, pp. 1184-1186). Taken together, these findings confirm that insect pollination is crucial to the plant's reproduction and progeny fitness.

Fire Ecology and Demography: Chamaecrista lineata
var.
keyensis
grows in the understory of pine rocklands, a fire-dependent ecosystem. The seeds have a hard seed coat that may help them survive fire (Liu
et al.
2005a, p. 216). Fire has important effects on survival and regeneration of
C. lineata
var.
keyensis.
Fire may immediately kill some of the plants, but populations rebound during the first and second years after fire. Three years post-fire, survival in burned areas can equal that of unburned areas, suggesting that
C. lineata
var.
keyensis
can recover completely after fire. Fire stimulates stem growth, fruiting, and seedling establishment. Fire seasonality may produce different responses in
C. lineata
var.
keyensis.
Overall, winter and early summer fires produce more favorable results compared with late summer fires (Liu and Menges 2005, p. 1848).

Demographic modeling by (Liu
et al.
2005a, p. 210) found that fire return intervals of 5 to 7 years generated the lowest extinction and population decline probabilities for
Chamaecrista lineata
var.
keyensis,
regardless of burn season. Bradley and Saha (2009, p. 20) found that both fire frequency and time since the last fire had significant effects on the density of
C. lineata
var.
keyensis
in study plots. The highest densities were found in plots that were burned three or more times over a 45-year period from 1960 to 2005, and in plots that had burned recently, while lower densities were associated with plots that had not been burned in 45 years.

Liu
et al.
(2005b, p. 71) found that differences in fire intensity (as measured by maximum ground temperature) did not have a significant long-term effect on survival, growth, or seedling recruitment. However, the number of fruits produced and percentage of fruiting plants increased as fire intensity increased. This suggests that low-intensity fires associated with shorter fire return intervals (less than 3 years) may not provide the most favorable conditions for post-fire recovery.

Taken together, these results indicate that
Chamaecrista lineata
var.
keyensis
can tolerate and may benefit from periodic fire. As discussed above under “Habitat,” fire is a crucial element in maintaining the pine rocklands habitat. Periodic fires eliminate the shrub subcanopy, remove litter from the ground, recycle nutrients, and are necessary to prevent succession to a hardwood-dominated ecosystem (rockland hammock) that is unsuitable for
C. lineata
var.
keyensis
(Bradley and Gann 1999, pp. 17-18).

Chamaesyce deltoidea
ssp.
serpyllum
(wedge spurge)

Species Description

Chamaesyce deltoidea
ssp.
serpyllum
is a small, prostrate, perennial herb. The stems are slender and numerous, radiating out from the taproot. The leaves are 2 to 5 mm (0.08 to 0.19 in) long, more or less triangular, and covered with fine short fuzz, giving the plant a silvery appearance. The flowers are cyathia, the specialized inflorescences characteristic of the genus
Euphorbia
and its close relatives. The fruit is a capsule about 1.5 mm (0.06 in) wide (Small 1933, p. 795; Herndon 1993, p. 50).

Taxonomy

John K. Small collected plants on Big Pine Key and first described
Chamaesyce deltoidea
ssp.
serpyllum
as
C. serpyllum
(Small 1913, p. 81). Burch (1966, p.99) included
C. serpyllum
as a subspecies of
C. deltoidea,
assigning the currently accepted name
C. deltoidea
ssp.
serpyllum.
The online Atlas of Florida Vascular Plants uses the name
C. deltoidea
ssp.
serpyllum
(Wunderlin and Hansen 2008, p. 1), and the Integrated Taxonomic Information System (ITIS 2015, p. 1) indicates that its taxonomic status is accepted. We have carefully reviewed all taxonomic data to determine that
Chamaesyce deltoidea
(Engelm. ex Chapm.) Small ssp.
serpyllum
(Small) D.G. Burch is a valid taxon. Synonyms include
Chamaesyce serpyllum
Small;
Euphorbia deltoidea
Engelmann ex Chapman ssp.
serpyllum
(Small) Y. Yang; and
Chamaesyce serpyllum
Small,
Euphorbia deltoidea
Engelmann ex Chapman var.
serpyllum
(Small) Oudejans (Wunderlin and Hansen 2008, p. 3).

Climate

The climate of south Florida where
Chamaesyce deltoidea
ssp.
serpyllum
occurs is classified as tropical savanna, as described above for
Chamaecrista lineata
var.
keyensis
.

Habitat

Chamaesyce deltoidea
ssp.
serpyllum
occurs in pine rocklands and adjacent disturbed sites on Big Pine Key, including roadsides. It most often grows directly from crevices in the oolitic limestone substrate (Bradley and Gann 1999, p. 31). Pine rocklands are described in detail for
Chamaecrista lineata
var.
keyensis,
above. Within pine rocklands,
Chamaesyce deltoidea
ssp.
serpyllum
is associated with areas of relatively higher elevation, extensive exposed rock substrate, where the understory is open, hardwood and palm density is low, and native herbaceous species cover and richness are high (Bradley and Saha 2009, p. 26; Ross and Ruiz 1996, p. 6; Bradley 2006, p. 27). Roadsides dominated mostly by native herbs and grasses where exotic lawn grasses are not established are a potentially important habitat for
C. deltoidea
ssp.
serpyllum
(Bradley 2006, p. 37).

Historical Range

Chamaesyce deltoidea
ssp.
serpyllum
is historically known from only Big Pine Key in the Florida Keys in Monroe County, Florida.

Current Range, Population Estimates, and Status

The current range of
Chamaesyce deltoidea
ssp.
serpyllum
is on Big Pine Key. Small groups of plants are scattered widely across the island (Herndon 1993, in Bradley and Gann 1999, p. 31).

Population data for
Chamaesyce deltoidea
ssp.
serpyllum
have been collected on Big Pine Key periodically since 1996. Indicators show that the population on Big Pine Key has declined over the past 19 years. Using study plots across Big Pine Key, Ross and Ruiz (1996, p. 6) found
C. deltoidea
ssp.
serpyllum
was present in 22 percent of study plots in 1996. When sampled again by Bradley (2006, p. 11; Bradley
et al.
2015, p. 21) in 2005, 2007, and 2013, the species was present in 7.4, 5.5, and 3.7 percent of study plots, respectively. This represents an 83 percent reduction of the species' frequency in study plots from 1996 to 2013, and a 50 percent reduction from 2005 to 2013. The decrease in frequency is attributed in large part to the total disappearance of the species from study plots in the southern portion of Big Pine Key after Hurricane Wilma in 2005 (Bradley
et al.
2013, p. 24).

Total population size for
Chamaesyce deltoidea
ssp.
serpyllum
on publicly owned pine rocklands on Big Pine Key (478 ha (1,181 acres)) was estimated to be 352,993 plants in 2005 (pre-Hurricane Wilma), 343,255 in 2007 (post-Wilma), and 368,557 in 2013. This represents a slight (4.4 percent) increase in the known population size of from 2005 to 2013 (Bradley
et al.
2013, p. 21). The slight increase in 2013 is due to the Blue Hole Fire in 2011. Prior to this fire, the species had not been detected in plots in the Blue Hole area of Big Pine Key, but was found in one plot after the 2011 fire. This single plot contained 134 plants, 17.3 percent of the plants recorded across all 646 plots in 2013. If this single plot is taken out of the analysis, density per plot would be 1.3, 10.3 percent lower than that recorded in 2005, and 18.6 percent lower than 2007 (Bradley
et al.
2015, pp. 24-25; Bradley and Saha 2009, p. 12). Since 82 percent of the pine rocklands on Big Pine Key are publicly owned, this estimate likely accounts for the majority of the population. Taken together, the data suggest that the population declined significantly due to Hurricane Wilma but rebounded by 2013. However, the frequency of the plant in study plots has decreased from 1996 to 2013, suggesting that fewer areas now support the species. While there have been significant changes between sampling events, the 9-year pattern of total population size is stable (Bradley
et al.
2015, pp. 21, 24, 49). At the same time, there has been a reduction in the species' range on Big Pine Key and frequency of the plant in study plots (Bradley
et al.
2015, pp. 25, 49), suggesting that while there has been a small increase in the total number of plants, the area occupied by the plant is shrinking.

Table 2 summarizes the status and trends of the known occurrences of
Chamaesyce deltoidea
ssp.
serpyllum.

Table 2—Summary of the Status and Trends of the Known Occurrences of Chamaesyce deltoidea ssp. serpyllum

Population
Ownership

Most recent population
estimate

Status
Trend

Big Pine Key
USFWS, FWC, private

368,557
1

Extant
1

Declining.
1

1
Bradley
et al.
2015, pp. 24-25.

Biology

Life History and Reproduction:
Reproduction is sexual, and the plant produces seeds. No studies of reproductive biology or ecology have been conducted for
Chamaesyce deltoidea
ssp.
serpyllum.
Other species of
Chamaesyce
are completely reliant on insects for pollination and seed production, while others are capable of self-pollination. Pollinators may include bees, flies, ants, and wasps (Ehrenfeld 1976, pp. 406, 95-97).

Fire Ecology and Demography:
The assemblage of endemic plants of the pine rocklands, which includes
Chamaesyce deltoidea
ssp.
serpyllum,
tends to be shade-intolerant and benefits from periodic burning to reduce competition from woody vegetation

(
e.g.,
shading, leaf litter accumulation) (Carlson
et al.
1993, p. 922; Liu
et al.
2005a, p. 210, Liu
et al.
2005b, p. 71).
C. deltoidea
ssp.
serpyllum
is found more frequently in recently burned areas (Slapcinsky
et al.
2010, p. 11). Populations of
C. deltoidea
ssp.
serpyllum
may decline without periodic fires, and fire has been shown to stimulate significant population growth (Slapcinsky and Gordon 2007, p. 5).

Linum arenicola
(sand flax)

Species Description

Linum arenicola
is a small, perennial herb that is 35 to 53 cm (14 to 21 in) tall with yellow flowers that are similar in appearance those of a buttercup (
Ranunculus
spp.). When not in flower, it resembles a short, wiry grass. Plants have one to several stems arising from their base. Leaves are linear in shape, 7-10 millimeters (mm) (0.3-0.4 in) long, 0.6-1 mm (0.02-0.04 in) wide, and arranged alternately along stems, and they have glands scattered along their edges. Flowers are produced on stems consisting of a few slender, spreading branches. The individual flowers are on small stalks 2 mm (0.08 in) long or shorter. The flowers have five yellow, egg-shaped petals that are 4.5-5.5 mm (0.18-0.22 in) long, and five green, lance-shaped to egg-shaped sepals that are 2.4-3.2 mm (0.09-0.13 in) long. The fruit is a woody capsule, 2.1-2.5 mm (0.08-0.1 in) long, 2-2.3 mm (0.08-0.09 in) diameter, which dries and splits into 10 segments. The seeds are ovate, 1.2-1.4 mm (0.05-0.06 in) long, and 0.7- 0.8 mm (0.027-0.031 in) wide (Rogers 1963, pp. 103-104).

Taxonomy

Linum arenicola
was first described by Small in 1907 as
Cathartolinum arenicola
from plants he collected in Miami-Dade County in 1904. This treatment was consistently followed by Small (1913a, p. 69; 1913b, p. 96; 1933, p. 752). In 1931, Winkler included
Cathartolinum
within the genus
Linum,
renaming the plants
Linum arenicola
(Winkler 1931, p. 30). Others have followed this treatment, including Rogers (1963, p. 103), Long and Lakela (1971, p. 505), Robertson (1971, p. 649), Wunderlin (1998, p. 100), and Wunderlin & Hansen (2003, p. 100) (Hodges and Bradley 2006, p. 37).

Synonyms include
Cathartolinum arenicola
Small (Wunderlin and Hansen 2004, p. 5). The Integrated Taxonomic Information System (2015, p. 1) uses the name
Linum arenicola
and indicates that this species' taxonomic standing is accepted. The online Atlas of Florida Vascular Plants (Wunderlin and Hansen 2008, p. 1) uses the name
L. arenicola.
There is consensus that
L. arenicola
is a distinct taxon. We have carefully reviewed the available taxonomic information to reach the conclusion that the species is a valid taxon.

Climate

The climate of south Florida where
Linum arenicola
occurs is classified as tropical savanna, as described above for
Chamaecrista lineata
var.
keyensis
and
Chamaesyce deltoidea
ssp.
serpyllum
.

Rainfall within the range of
Linum arenicola
varies from an annual average of 153-165 cm (60-65 in) in the northern portion of the Miami Rock Ridge to an average of 89-102 cm (35-40 in) in the lower Florida Keys (Snyder
et al.
1990, p. 238).

Habitat

Pine Rockland
s:
Linum arenicola
occurs in pine rocklands, disturbed pine rocklands, dry marl prairie, and disturbed areas on rocky soils adjacent to these habitats (Bradley and Gann 1999, p. 61; Hodges and Bradley 2006, p. 37).
L. arenicola
grows in thin soil over limestone or in small soil patches caught in surface irregularities of exposed limestone (Kernan and Bradley, 1996, p. 2). Sites most likely to support
L. arenicola
have a grass- and herb-dominated understory, abundant pine regeneration, and high cover of exposed rock (Ross and Ruiz 1996, pp. 5-6). The pine rocklands and marl prairies where this species occurs require periodic fire to maintain an open, shrub-free subcanopy, and to reduce litter levels (Bradley and Saha 2009, p. 4). Pine rocklands habitat is described in detail for
Chamaecrista lineata
var.
keyensis,
above.

Roadsides and Other Disturbed Sites:
While pine rocklands historically were the primary habitat of
Linum arenicola,
the species is currently rare in relatively undisturbed pine rocklands, with the exception of plants on Big Pine Key. Several occurrences are in scraped (scarified) pine rocklands remnants that are dominated by native pine rocklands species, but have little or no pine canopy or subcanopy (Bradley and Van Der Heiden 2013, pp. 9-12). Two populations in Miami-Dade County occur entirely on levees composed of crushed oolitic limestone that are surrounded by sawgrass marsh (Bradley and Gann 1999, p. 61; Bradley and Van Der Heiden 2013, pp. 7-9). Roadsides and other disturbed sites are important habitat for
L. arenicola
because they imitate upland herbaceous habitat (Hodges and Bradley 2006, p. 40). The most robust roadside populations occur in areas adjacent to pine rocklands or rockland hammocks (Hodges 2010, p. 3). Where
L. arenicola
is found on roadsides, the ground cover is dominated mostly by native herbs and grasses where exotic lawn grasses have not been planted (Bradley 2006, p. 37). Infrequent mowing of some roadsides, and of disturbed sites such as Homestead Air Reserve Base (HARB) and U.S. Special Operations Command South Headquarters (SOCSOUTH), a unified command of all four services in the Department of Defense (DOD) has likely allowed the species to persist by preventing these sites from being taken over by hardwoods.

Because
Linum arenicola
seems to only rarely occur within intact pine rocklands, but more frequently adjacent to this habitat, developing conservation and management plans for this species is exceptionally difficult. Its persistence on roadsides is not fully understood.
L. arenicola
was at one time more common in pine rocklands in Miami-Dade County, but a lack of periodic fires in most pine rocklands fragments over the last century have pushed this species into more sunny, artificial environments (Bradley and Gann 1999, p. 61). It is also possible that the species has evolved to persist along roadsides as fire regimes and natural areas were altered and destroyed over the last century (Hodges and Bradley 2006, p. 41).

Dry Marl Prairie:
Marl prairie is a sparsely vegetated, grass-dominated community found on marl substrates in South Florida. Marls are fine, white, calcareous muds formed from calcite precipitated by a mixture of green algae, blue green algae, and diatoms, known as periphyton. It is seasonally inundated (2 to 4 months) to a shallow depth averaging about 20 cm (8 in). Marl prairie is a diverse community that may contain over 100 species. Marl prairie normally dries out during the winter and is subject to fires at the end of the dry season (FNAI 2010, p. 1). Occurrences reported from marl prairie are at sites that have been artificially drained (Bradley and Van Der Heiden 2013, p. 11), or are scraped pine rocklands that function more like marl prairie (Kernan and Bradley 1996, p. 11). As with roadside populations of
Linum arenicola,
it is possible that dry marl prairies have become refugia for the species as fire regimes and natural areas were altered and destroyed over the last century. Accordingly, the Service does not consider marl prairie to be a primary habitat for
L. arenicola
.

Historical Range

The historical range of
Linum arenicola
consists of central and southern Miami-Dade County and

Monroe County in the lower Florida Keys (Bradley and Gann 1999, p. 61). In Miami-Dade County, records for the species were widespread from the Coconut Grove area to the southern part of the County, close to what is now the main entrance to Everglades National Park and Turkey Point (Bradley and Gann 1999, p. 61). In the Florida Keys (Monroe County), there are records of the species from Big Pine Key, Ramrod Key, Upper and Lower Sugarloaf Keys, Park Key, Boca Chica Key, Middle Torch Key (Bradley and Gann 1999, p. 61), and Big Torch Key (Hodges 2010, p. 10).

Current Range, Population Estimates, and Status

The current range of
Linum arenicola
consists of eight extant populations in Miami-Dade County and four extant populations in the Florida Keys (see Table 3, below). In Miami-Dade County, the current distribution of
Linum arenicola
is from just north of SW 184 Street (in the Richmond Pinelands), south to the intersection of Card Sound Road and the C-102 canal, and west to SW 264 Street and 177 Avenue (Everglades Archery Range at Camp Owaissa Bauer). This distance is approximately 30 km (19 mi) north to south, and 14 km (9 mi) east to west. In the Florida Keys (Monroe County), the current distribution of
L. arenicola
includes four islands: Big Pine Key, Upper and Lower Sugarloaf Keys, and Big Torch Key.

Multiple surveys have been conducted for
Linum arenicola
in Miami-Dade and Monroe Counties over the past 30 years. However, most surveys only cover one county and not the other. The large area of potential habitat and scarcity and diminutive size of
L. arenicola
make thorough surveys for this species difficult (Hodges and Bradley 2006, p. 37).

Based on a compilation of all survey work through 2013, including Austin (1980), Kernan and Bradley (1996, pp.1-30), Bradley and Gann (1999, pp. 61-65), Hodges and Bradley (2006, pp. 37-41), Bradley and Saha (2009, p. 10), Bradley (2009, p. 3), Hodges (2010, pp. 4-5, 15), Bradley and van der Heiden (2013, pp. 6-12,19), and Bradley
et al.
(2015, pp. 28-29), of 26 historical population records for
Linum arenicola,
12 populations are extant and 14 are extirpated (see Table 3), a loss of roughly 54 percent of known populations, from the early 1900s to the present.

Table 3 summarizes the status and trends of the known occurrences of
Linum arenicola
.

Table 3—Summary of the Status and Trends of the Known Occurrences of Linum arenicola

Population
Ownership

Most recent population
estimate

County
Trend

Extant 12 records

Big Pine Key

USFWS, FWC, TNC
12
, Private

2,676 (2007)
1

Monroe
declining.

Upper Sugarloaf Key

FDOT
13
, USFWS

73 (2010)
2

Monroe
insufficient data.

Lower Sugarloaf Key

FDOT
13
, USFWS

531 (2010)
2

Monroe
stable.

Big Torch Key

FDOT
13
, Private

1 (2010)
2

Monroe
declining.

Richmond Pineland
Private

56 (2014)
5

Miami-Dade
insufficient data.

Martinez Pineland
Miami-Dade County

100-200 (2013)
6

Miami-Dade
insufficient data.

Everglades Archery Range (Camp Owaissa Bauer)
Miami-Dade County

23 (2012)
7

Miami-Dade
insufficient data.

HAFB
15
1—S of Naizare BLVD

DOD
14
, Miami-Dade County

24,000 (2013)
7

Miami-Dade
stable.

SOCSOUTH (HAFB 2—NW side of Bikini BLVD)

DOD
14
(leased from Miami-Dade County)

74,000 (2009)
7 10

Miami-Dade
stable.

HARB (SW 288 St. and 132 Ave)

DOD
14

37 (2011)
7

Miami-Dade
insufficient data.

C-102 Canal SW 248 St. to U.S. 1

SFWMD
11

1,000-10,000 (2013)
7

Miami-Dade
insufficient data.

L-31E canal, from SW 328 St. to Card Sound Road

SFWMD
11

Plants occur along 14 km (8.7 mi) of levee (2013)
7

Miami-Dade
insufficient data.

Extirpated 14 records

Middle Torch Key

FWC, FDOT
13

3 (2005)
3

Monroe

Ramrod Key

FDOT
13

110 (1979)
4

Monroe

Park Key

FDOT
13

unknown (1961)
3

Monroe

Boca Chica

DOD
14
, other (unknown)

unknown (1912)
3

Monroe

Camp Jackson
unknown

unknown (1907)
9

Miami-Dade

Big Hammock Prairie
unknown

unknown (1911)
9

Miami-Dade

Camp Owaissa Bauer
Miami-Dade County

10 (1983)
7

Miami-Dade

Allapatah Drive and Old Cutler Road
Private

256 (1996)
8

Miami-Dade

Bauer Drive (Country Ridge Estates)
Miami-Dade County

8 (1996)
8

Miami-Dade

Silver Green Cemetery
Private

47 (1996)
8

Miami-Dade

Palmetto Bay Village Center
Private

12 (1996)
8

Miami-Dade

HAFB (Community Partnership Drive)

DOD
14
, Miami-Dade County

unknown (2010)
7

Miami-Dade

Coco Plum Circle (corner of Robles Street & Vista Mar Street)
Private

75 (1996)
8

Miami-Dade

George Avery Pineland Preserve
Private

“small colony” (2002)
7

Miami-Dade

1
Bradley and Saha 2009, p. 10

2
Hodges 2010, p. 10

3
Hodges and Bradley 2006, pp. 39-48

4
Austin
et al.
1980 in FNAI

5
FTBG 2014, p. 2

6
Possely 2014, pers. comm.

7
Bradley and Van Der Heiden 2013, pp. 6-11

8
Kernan and Bradley 1996, p. 9

9
Bradley and Gann 1999, p. 65

10
Bradley 2009, p. 3

11
South Florida Water Management District (SFWMD)

12
The Nature Conservancy (TNC)

13
Florida Department of Transportation (FDOT)

14
Department of Defense (DOD)

15
Homestead Air Force Base (HAFB; decommissioned)

Based on the data presented in Table 3, reliable population trends can be derived from past surveys for 5 of the 12 extant populations. Populations on Big Pine Key and Big Torch Key have shown clear declines. Three populations appear to be stable (data suggest they have not declined appreciably). Data are insufficient to determine trends for the remaining seven populations. The data also show that 5 of the 12 extant populations are rather small, having fewer than 100 plants.

Miami-Dade County:
The first survey for
Linum arenicola,
conducted in 1980 in Miami-Dade County, reported two extant and eight extirpated populations, but population sizes were not reported (Austin
et al.,
1980, p. 3). A 1996 survey conducted in Miami-Dade County reported seven populations, representing about 1,000 plants (Kernan and Bradley 1996, p. 5). A 1999 status survey reported five extant populations and seven extirpated populations in Miami-Dade County (Bradley and Gann 1999, p. 65).

A comprehensive field survey of
Linum arenicola
sites in Miami-Dade was conducted in 2013 (Bradley and van der Heiden 2013, p. 4).
L. arenicola
populations were found at six sites, containing an estimated total of 107,060 plants. Populations ranged in size from 23 plants to 74,000 plants, with a median population size of approximately 4,500. All but one of the Miami-Dade
L. arenicola
populations occur on public lands, but only the Martinez Pineland site is managed for conservation. The remaining sites are owned by the DOD (military bases), State of Florida (canal banks; SFWMD), and Miami-Dade County (a public archery range). A seventh small population located in 2014 at the Richmond pinelands is located on private land that is currently slated for development (Fairchild Tropical Botanic Garden (FTBG) 2014, p. 2). The largest
Linum arenicola
population in Miami-Dade County, estimated at 74,000 plants in 2009 (Bradley 2009, p. 3), is located on property owned by the Miami-Dade County Homeless Trust and leased to Special Operations Command South (SOCSOUTH; a DOD facility).

In Miami-Dade County, of 18 records for
Linum arenicola,
8 populations are extant, while 10 are extirpated, a loss of roughly 56 percent of known populations. The loss of these populations corresponds to a contraction of the species' historical range in Miami-Dade County by approximately 20 km (12 mi) at its northern extent (40 percent reduction in north to south range), and approximately 15 km (9 mi) of its east to west extent (50 percent reduction in east to west range).

Monroe County (Florida Keys):
A 1999 status survey reported four
Linum arenicola
populations in Monroe County (Bradley and Gann 1999, p. 65). In 2006, Hodges and Bradley (2006, pp. 37-41) conducted the first comprehensive survey of the distribution and abundance of
L. arenicola
in the Florida Keys, including extant occurrences, historical records, and exploratory surveys of potential habitat. Four extant populations were observed (Big Pine Key, Big Torch Key, Middle Torch Key, and Lower Sugarloaf Key) and three historical populations were confirmed extirpated (Boca Chica Key, Ramrod Key, and Park Key). The surveys did not find
L. arenicola
in potential habitat on No Name Key, Little Torch Key, or Upper Sugarloaf Key (Hodges and Bradley 2006, pp. 37, 48). However, in 2010, Hodges (2010, p. 10) resurveyed Upper Sugarloaf and rediscovered the population.

Linum arenicola
is extirpated from 4 of 8 (50 percent) of the islands that once supported it. Its historical range spanned approximately 36 km (22 mi) from northeast to southwest. The loss of populations on Boca Chica, Park, Middle Torch, and Ramrod Keys represents a 14-km (9-mi) loss of the western extent of the species' range, corresponding to a 39 percent contraction of the species' historical range.

The total population of
Linum arenicola
in Monroe County is estimated at 2,676 plants in pine rocklands on Big Pine Key (Bradley and Saha 2009, p. 10), and 100 to 1,000 plants across the remainder of the Florida Keys (Hodges and Bradley 2006, pp. 37, 48; Hodges 2010, p. 10).

The largest population in Monroe County is located on Big Pine Key within the National Key Deer Refuge (NKDR) and surrounding lands, where there are approximately 478 ha (1,181 ac) of publicly owned pine rocklands (Gann
et al.
2002, p. 806; Bradley 2006, p. 4; Hodges and Bradley 2006, pp. 37-38). It is also the best studied population. On Big Pine Key,
Linum arenicola
occurs at the Terrestris Preserve, which is owned by TNC; this occurrence is included within the Big Pine Key site in Table 3.

Linum arenicola
on Big Pine Key has been surveyed multiple times since 1996, with the most recent being 2014. Because of the size of Big Pine Key, sample study plots were utilized for these surveys, as opposed to a complete search of all potential habitats. Ross and Ruiz (1996, p. 5) found the species in 11 percent of their study plots. Subsequent surveys in 2005, 2007, and 2013 have found
L. arenicola
to be extremely rare, being recorded in 4.1, 2.0, and 1.4

percent of study plots, respectively, representing an 87 percent reduction from 1996 to 2013 (Bradley
et al.
2015, pp. 28-29).

The decline in the Big Pine Key population of
Linum arenicola
from 2005 to 2007 can be largely attributed to the effects of Hurricane Wilma (Bradley 2006, p. 11; Hodges 2010, p. 4). Prior to Wilma, there was a maximum of 56,404 individuals of
L. arenicola
in the 478 ha (1,181 ac) of publicly owned pine rocklands on Big Pine Key (Bradley 2006, p. 19). As of 2007, there were just 2,676 plants, representing a 95 percent decline (Bradley and Saha 2009, p. 10). Significantly, the species virtually disappeared from the southern half of Big Pine Key after Hurricane Wilma (Bradley and Saha 2009, p. 10).

Historically, the population has declined due to habitat loss and fire suppression. Approximately half of the historical pine rocklands on Big Pine Key have been lost (Bradley 2006, p. 35). Long-term ecological changes associated with fire suppression, land clearing, SLR, changes in hydrology, fluctuations in Key deer (
Odocoileus virginianus clavium
) densities, and invasion of exotic plants likely have impacted the population sizes of this species (Bradley 2006, p. 2; Bradley and Saha 2009, p. 2).

The population on Big Torch Key also declined after Hurricane Wilma, but this decline may have been due to herbicide applications or frequent mowing associated with road shoulder maintenance (Hodges 2010, p. 4).

Biology

Life History and Reproduction:
Little is known about the life history of
Linum arenicola,
including pollination biology, seed production, or dispersal. Reproduction is sexual, with new plants generated from seeds. The species produces flowers from February to September, with a peak around March and April.
L. arenicola
population demographics or longevity have not been studied (Bradley and Gann, 1999, p. 65; Hodges and Bradley 2006, p. 41; Hodges 2007, p. 2).

Fire Ecology and Demography:
There have been no studies of
Linum arenicola
population demographics or relationship to fire, though historical declines have been partially attributed to habitat loss from fire suppression or inadequate fire management.

Argythamnia blodgettii
(Blodgett's silverbush)

Species Description

Argythamnia blodgettii,
in the Euphorbia family, is an erect, perennial shrub or herb, 10 to 60 cm (4 to 24 in) tall, with a woody base and small, green flowers. The stems and leaves are covered with small hairs. The leaves, arranged alternately along the stems, are 1.5 to 4.0 cm (0.6 to 1.6 in) long, have smooth (or rarely toothed) edges, are oval or elliptic in shape, and often are colored a distinctive, metallic bluish green. The plants have separate male and female flowers. Staminate (male) flowers have a calyx 7 to 8 mm (0.27 to 0.31 in) wide, consisting of 4 to 5 lance-shaped sepals that are larger than the petals. The petals are broadly elliptic and shorter than the sepals. There are 10 stamens. Pistillate (female) flowers have 4 to 5 sepals that are 5 to 6 mm (0.19 to 0.24 in) long, lance-shaped, and often more narrow than those of male flowers. The petals are broadly elliptic, shorter than the sepals. The fruit is a woody capsule 4 to 5 mm (0.16 to 0.19 in) wide, which contains the seeds (Adapted from Small 1933, pp. 784-785; Bradley and Gann 1999, p. 2).

Taxonomy

Botanist John Torrey first described the species in Chapman (1884, p. 100) as
Aphora blodgettii,
reporting it for South Florida. In an 1896 (p. 100) revision of the genus, Pax placed it in the genus
Ditaxis.
In 1897 (p. 100), Chapman placed it in the genus
Argythamnia.
In 1903, Small placed it again in the genus
Ditaxis.
In 1914, Pax (p. 100) placed it in synonymy under
Ditaxis fendleri,
a plant of Colombia, Venezuela, Curacao, and Trinidad. Small (1933, pp. 784-785) retained it as
Ditaxis blodgettii,
treating it as a southern Florida endemic. Subsequent authors (Webster 1967, p. 100; Long and Lakela 1971, p. 558; Wunderlin 1998, p. 100; Wunderlin and Hansen 2003, p. 100) have retained it as a southern Florida endemic
Argythamnia blodgettii
(from Hodges and Bradley 2006, p. 10).

The Integrated Taxonomic Information System (2015, p. 1) uses the name
Argythamnia blodgettii
and indicates that this species' taxonomic standing is accepted. The online Atlas of Florida Vascular Plants (Wunderlin and Hansen 2008, p. 1) uses the name
A. blodgettii.
In summary, there is consensus that
A. blodgettii
is a distinct taxon. We have carefully reviewed the available taxonomic information to reach the conclusion that the species is a valid taxon. Synonyms include
Aphora blodgettii
Torr. ex Chapm.;
Ditaxis blodgettii
(Torr. ex Chapm.) Pax;
Argyrothamnia blodgettii
(Torr. ex Chapm.) Chapm.; and
Ditaxis fendleri
Pax, not (Müll. Arg.) Pax and K. Hoof.

Climate

The climate of south Florida where
Argythamnia blodgettii
occurs is classified as tropical savanna, as described above for
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum,
and
Linum arenicola.

Rainfall within the range of
Argythamnia blodgettii
varies from an annual average of 153-165 cm (60-65 in) in the northern portion of the Miami Rock Ridge to an average of 89-102 cm (35-40 in) in the lower Florida Keys (Snyder
et al.
1990, p. 238).

Habitat

Argythamnia blodgettii
grows in pine rocklands, in sunny gaps or edges of rockland hammock and coastal berm, and on roadsides (Bradley and Gann 1999, p. 3). It grows from crevices on oolitic limestone or on sand. The pine rocklands habitat where it occurs requires periodic fire to maintain an open, sunny understory with a minimum amount of hardwoods. Bradley and Gann (1999, p. 3) indicated that this species does tolerate some degree of human-induced disturbance. It can often be found along disturbed edges of pine rocklands, rockland hammock, and coastal berm, or in completely scarified pine rocklands (Bradley and Gann, 1999, p. 3). Pine rocklands are described in detail for
Chamaecrista lineata
var.
keyensis,
above.

Coastal Berm:
Coastal berms are landscape features found along low-energy coastlines in south Florida and the Florida Keys. Coastal berm is a short forest or shrub thicket found on long, narrow, storm-deposited ridges of loose sediment formed by a mixture of coarse shell fragments, pieces of coralline algae, and other coastal debris. These ridges parallel the shore and may be found on the seaward edge or landward edge of the mangroves or farther inland depending on the height of the storm surge that formed them. They range in height from 0.30 to 3.05 m (1 to 10 ft). Structure and composition of the vegetation is variable depending on height and time since the last storm event. The most stable berms may share some tree species with rockland hammocks, but generally have a greater proportion of shrubs and herbs. Tree species may include
Bursera simaruba
(gumbo limbo),
Coccoloba uvifera
(seagrape),
Coccothrinax argentata
(silver palm),
Guapira discolor
(blolly),
Drypetes diversifolia
(milkbark),
Genipa clusiifolia
(seven year apple), and
Metopium toxiferum
(poisonwood). Characteristic tall shrub and short tree

species include
Eugenia foetida
(Spanish stopper),
Ximenia americana
(hog plum),
Randia aculeata
(white indigoberry),
Pithecellobium keyense
(Florida Keys blackbead), and
Sideroxylon celastrinum
(saffron plum). Short shrubs and herbs include
Hymenocallis latifolia
(perfumed spiderlily),
Capparis flexuosa
(bayleaf capertree),
Lantana involucrata
(buttonsage), and
Rivina humilis
(rougeplant). More seaward berms or those more recently affected by storm deposition may support a suite of plants similar to beaches, including shoreline
Sesuvium portulacastrum
(sea purslane),
Distichlis spicata
(saltgrass), and
Sporobolus virginicus
(seashore dropseed), or scattered to dense shrub thickets with
Conocarpus erectus
(buttonwood
),
stunted
Avicennia germinans
(black mangrove),
Rhizophora mangle
(red mangrove),
Laguncularia racemosa
(white mangrove),
Suriana maritima
(bay cedar),
Manilkara jaimiqui
(wild dilly),
Jacquinia keyensis
(joewood), and
Borrichia frutescens
(bushy seaside oxeye) (Florida Natural Areas Inventory (FNAI) 2010a, p. 1).

Coastal berms are deposited by storm waves along low-energy coasts. Their distance inland depends on the height of the storm surge. Tall berms may be the product of repeated storm deposition. Coastal berms that are deposited far enough inland and remain long-undisturbed may in time succeed to hammock. This is a structurally variable community that may appear in various stages of succession following storm disturbance, from scattered herbaceous beach colonizing plants to a dense stand of tall shrubs (FNAI 2010a, p. 2).

Rockland Hammock:
Rockland hammock is a species-rich, tropical hardwood forest on upland sites in areas where limestone is very near the surface and often exposed. The forest floor is largely covered by leaf litter with varying amounts of exposed limestone and has few herbaceous species. Rockland hammocks typically have larger, more mature trees in the interior, while the margins can be almost impenetrable in places with dense growth of smaller shrubs, trees, and vines. Typical canopy and subcanopy species include
Bursera simaruba, Lysiloma latisiliquum
(false tamarind),
Coccoloba diversifolia
(pigeon plum),
Sideroxylon foetidissimum
(false mastic),
Ficus aurea
(strangler fig),
Piscidia piscipula
(Jamaican dogwood),
Ocotea coriacea
(lancewood),
Drypetes diversifolia, Simarouba glauca
(paradisetree),
Sideroxylon salicifolium
(willow bustic),
Krugiodendron ferreum
(black ironwood),
Exothea paniculata
(inkwood),
Metopium toxiferum,
and
Swietenia mahagoni
(West Indies mahogany). Mature hammocks may be open beneath a tall, well-defined canopy and subcanopy. More commonly, in less mature or disturbed hammocks, dense woody vegetation of varying heights from canopy to short shrubs is often present. Species that generally make up the shrub layers within rockland hammock include several species of
Eugenia
(stoppers),
Thrinax morrisii
and
T. radiata
(thatch palms),
Amyris elemifera
(sea torchwood),
Ardisia escallonioides
(marlberry),
Psychotria nervosa
(wild coffee),
Chrysophyllum oliviforme
(satinleaf),
Sabal palmetto
(cabbage palm),
Guaiacum sanctum
(lignum-vitae),
Ximenia americana, Colubrina elliptica
(soldierwood),
Pithecellobium unguis-cati
and
Pithecellobium keyense, Coccoloba uvifera,
and
Colubrina arborescens
(greenheart). Vines can be common and include
Toxicodendron radicans
(eastern poison ivy),
Smilax auriculata
(earleaf greenbrier),
Smilax havanensis
(Everglades greenbrier),
Parthenocissus quinquefolia
(Virginia creeper),
Hippocratea volubilis
(medicine vine), and
Morinda royoc
(redgal). The typically sparse short shrub layer may include
Zamia pumila
(coontie) and
Acanthocereus tetragonus
(triangle cactus). Herbaceous species are occasionally present and generally sparse in coverage. Characteristic species include
Lasiacis divaricata
(smallcane),
Oplismenus hirtellus
(basketgrass), and many species of ferns (FNAI 2010e, p. 1).

Rockland hammock occurs on a thin layer of highly organic soil covering limestone on high ground that does not regularly flood, but it is often dependent upon a high water table to keep humidity levels high. Rockland hammocks are frequently located near wetlands; in the Everglades, they can occur on organic matter that accumulates on top of the underlying limestone; in the Keys, they occur inland from tidal flats (FNAI 2010e, p. 1).

Rockland hammock is susceptible to fire, frost, canopy disruption, and ground water reduction. Rockland hammock can be the advanced successional stage of pine rocklands, especially in cases where rockland hammock is adjacent to pine rocklands. In such cases, when fire is excluded from pine rocklands for 15 to 25 years, it can succeed to rockland hammock vegetation. Historically, rockland hammocks in south Florida evolved with fire in the landscape. Fire most often extinguished near the edges when it encountered the hammock's moist microclimate and litter layer. However, rockland hammocks are susceptible to damage from fire during extreme drought or when the water table is lowered. In these cases, fire can cause tree mortality and consume the organic soil layer (FNAI 2010e, p. 2).

Rockland hammocks are also sensitive to the strong winds and storm surge associated with infrequent hurricanes. Canopy damage often occurs, which causes a change in the microclimate of the hammock. Decreased relative humidity and drier soils can leave rockland hammocks more susceptible to fire. Rockland hammock can transition into glades marsh, mangrove swamp, salt marsh, coastal rock barren, pine rocklands, maritime hammock, or marl prairie (FNAI 2010e, p. 2).

The sparsely vegetated edges or interior portions laid open by canopy disruption are the areas of rockland hammock that have light levels sufficient to support
Argythamnia blodgettii.
However, the dynamic nature of the habitat means that areas not currently open may become open in the future as a result of canopy disruption from hurricanes, while areas currently open may develop more dense canopy over time, eventually rendering that portion of the hammock unsuitable for
A. blodgettii.

Historical Range

Argythamnia blodgettii
historically occurred from central and southern Miami-Dade County from Brickell Hammock to Long Pine Key in Everglades National Park, and in Monroe County throughout the Florida Keys from Totten Key south to Key West (Bradley and Gann 1999, p. 2).

Current Range, Population Estimates, and Status

Argythamnia blodgettii
is currently known from central Miami-Dade County from Coral Gables and southern Miami-Dade County to Long Pine Key in Everglades National Park, and the Florida Keys from nine islands, from Windley Key (Bradley and Gann 1999, p. 3) southwest to Boca Chica Key (Hodges and Bradley 2006, pp. 10, 43).

Previous status surveys of
Argythamnia blodgettii
include Bradley and Gann (1999, pp. 2-6) and Hodges and Bradley (2006, pp. 11-20, 43). Bradley and Gann (1999, p. 3) reported 18 extant occurrences of
A. blodgettii
in 1999 (4 in Monroe County, 14 in Miami-Dade County), representing approximately 10,000 plants. Hodges and Bradley (2006, pp. 11-20, 43) verified that
A. blodgettii
is extant on nine islands in the Florida Keys

(Monroe County), and has an estimated population of between 10,000 and 100,000 plants (Hodges and Bradley, p. 2). The FNAI element tracking summary data indicated a total of 31 element occurrence records in 2 counties, with 24 occurrences in management areas (FNAI 2008, p. 1). There is insufficient data available to identify trends in any populations of
A. blodgettii.

Although we do not know the total extent of the former range of
Argythamnia blodgettii,
approximately 12 miles (19 kilometers) of the species' range has been lost near the northern end of the range in Miami-Dade County and 43 miles (69 kilometers) has been lost in Monroe County on the southern edge of the species' range (Bradley and Gann 1999, p. 3).

Miami-Dade County:
According to data from the Institute for Regional Conservation (IRC), the estimated population of
Argythamnia blodgettii
in Miami-Dade County is 375 to 13,650 plants (
i.e.,
total of low and high estimates) (K. Bradley 2007, pers. comm.); however, this may be an overestimate of the actual population size because it was based upon a log10 scale. In Everglades National Park (ENP), the current estimated population size is 2,000 plants (J. Sadle 2015, pers. comm.).

Based on the data presented below in Table 4, there are 31 records for
Argythamnia blodgettii
in Miami-Dade County. Six populations are extant, 11 are extirpated, and the status of 14 is uncertain because they have not been surveyed in 15 years or more.

Monroe County:
In the Keys,
Argythamnia blodgettii
is extant on nine islands, with three others of uncertain status (Hodges and Bradley 2006, p. 43). The largest population surveyed is on Big Munson Island and is estimated to be 8,000 to 9,000 plants (Hodges and Bradley 2006, p. 17). On Big Pine Key, a population of
A. blodgettii
estimated at 2,200 plants is found scattered across the island. Occurrences are known from the Koehn's subdivision, Long Beach, Cactus Hammock, and Watson Hammock. Sizable populations also occur at Key West Naval Air Station on Boca Chica Key. The total population size in the Florida Keys is estimated to be approximately 13,200 plants (Hodges and Bradley 2006, pp. 10-13, 17).

Argythamnia blodgettii
is extirpated from 3 of 16 (23 percent) of the islands that once supported it. Based on the data presented in Table 4, there are 18 records for
A. blodgettii
in Monroe County. Eleven populations are extant, three are extirpated, and the status of four is uncertain because they have not been surveyed in 15 years or more.

Table 4—Summary of the Status and Trends of the Known Occurrences of Argythamnia blodgettii

Population
Ownership

Most recent population
estimate

County
Trend

Extant 17 records

Plantation Key, Snake Creek Hammock
FWC

101-1,000 (2005)
2

Monroe
Insufficient data.

Lower Matecumbe Key—Klopp Tract

FDEP
6

11-100 (2000)
2

Monroe
Insufficient data.

Lignumvitae Key

FDEP
6

101-1,000 (2005)
2

Monroe
Insufficient data.

Big Munson Island
Private (Boy Scouts of America)

1,001-10,000 (2005)
2

Monroe
Insufficient data.

North Key Largo
DOD, FDOT

No estimate (2005)
8

Monroe
Insufficient Data.

Key Largo—Dove Creek Hammock
FWC, FDOT

11-100 (2005)
2

Monroe
Insufficient data.

Vaca Key (Marathon)—Blue Heron Hammock
FWC, FDOT

11-100 (2005)
2

Monroe
Insufficient data.

Windley Key—State Park

FDEP
6

11-100 (2005)
2

Monroe
Insufficient data.

Boca Chica KWNAS
7
Runway 25

DOD

1,001-10,000 (2004)
2

Monroe
Insufficient data.

Boca Chica Key KWNAS
7
Weapons Hammock

DOD

200 (2004)
2

Monroe
Insufficient data.

Big Pine Key
USFWS, FWC, private

~2,200 (2005)
2

Monroe
Insufficient data.

ENP Long Pine Key Deer Hammock area (Pine Block A), Turkey Hammock area (Pine Block B), Pine Block E

NPS
5

2,000 (2015)
4

Miami-Dade
Insufficient data.

Camp Choee
Private (Girl Scout Council of Tropical Florida)

3 (2005)
3

Miami-Dade
Insufficient data.

Crandon Park—Key Biscayne
Miami Dade Parks and Recreation

4 (2005)
3

Miami-Dade
Insufficient data.

Martinez Pineland/Larry and Penny Thompson Park
Miami Dade Parks and Recreation

6 (2005)
3

Miami-Dade
Insufficient data.

Tropical Park Pineland
Miami Dade Parks and Recreation

20 (2005)
3

Miami-Dade
Insufficient data.

Boystown Pineland
Private

No estimate (2005)
3

Miami-Dade
Insufficient data.

Uncertain 18 records

Crawl Key, Forestiera Hammock
Private

10 (1982)
3

Monroe
Insufficient data.

Long Key State Park
FDEP

No estimate (1999)
2

Monroe
Insufficient data.

Stock Island
Private

No estimate (1981)
2

Monroe
Insufficient data.

Boot Key
Private

11-100 (1998)
2

Monroe
Insufficient data.

Deering Estate
State of Florida

11-100 (1991)
1

Miami-Dade
Insufficient data.

Castellow Hammock
Miami Dade Parks and Recreation

11-100 (1991)
1

Miami-Dade
Insufficient data.

Owaissa Bauer County Park
Miami Dade Parks and Recreation

101-1,000 (1991)
1

Miami-Dade
Insufficient data.

Pine Ridge Sanctuary
Private

2-10 (1992)
1

Miami-Dade
Insufficient data.

County Ridge Estates
Private

11-100 (1999)
1

Miami-Dade
Insufficient data.

Epmore Drive pineland
Private

2-10 (1999)
1

Miami-Dade
Insufficient data.

Gifford Arboretum Pineland
Private

2-10 (1999)
1

Miami-Dade
Insufficient data.

Ned Glenn Nature Preserve
Miami Dade Parks and Recreation

11-100 (1999)
1

Miami-Dade
Insufficient data.

Natural Forest Community #317
Private

2-10 (1999)
1

Miami-Dade
Insufficient data.

Old Dixie pineland
Private

11-100 (1999)
1

Miami-Dade
Insufficient data.

Owaissa Bauer Addition #1
Miami Dade Parks and Recreation

11-100 (1991)
1

Miami-Dade
Insufficient data.

SW 184th St. and 83rd Ave.
Private

11-100 (1999)
1

Miami-Dade
Insufficient data.

Castellow #33
Private

12 (1995)
3

Miami-Dade
Insufficient data.

Castellow #31
Private

30-50 (1995)
3

Miami-Dade
Insufficient data.

Extirpated 14 records

Upper Matecumbe Key
unknown

No estimate (1967)
3

Monroe

Totten Key
NPS

No estimate (1904)
1

Monroe

Key West
City of Key West

No estimate (1965)
1

Monroe

Fuch's Hammock
Miami-Dade County

No estimate (1991)
1

Miami-Dade

Brickell Hammock
unknown

Extirpated 1937
1

Miami-Dade

Carribean Park
Miami-Dade County

Extirpated 1998
1

Miami-Dade

Coconut Grove
Miami-Dade County

Extirpated 1901
1

Miami-Dade

Coral Gables area
unknown

Extirpated 1967
1

Miami-Dade

Miller and 72nd Ave
unknown

Extirpated 1975
1

Miami-Dade

Orchid Jungle
Miami-Dade County

Extirpated 1930
1

Miami-Dade

Palms Woodlawn Cemetery
Private

Extirpated 1992
1

Miami-Dade

South of Miami River
unknown

Extirpated 1913
1

Miami-Dade

Bauer Drive Pineland
Private

No estimate (1985)
3

Miami-Dade

Naranja
Private

No estimate (1974)
3

Miami-Dade

1
Bradley and Gann 1999, p. 6.

2
Hodges and Bradley 2006, pp. 10-17.

3
FNAI 2011.

4
Sadle 2015, pers. comm., p. 1.

5
National Park Service (NPS).

6
Florida Department of Environmental Protection (FDEP).

7
Key West Naval Air Station (KWNAS).

8
Henize and Hipes 2005, p. 25.

Biology

Life History and Reproduction:
Reproductive biology of
Argythamnia blodgettii
has not been studied. Reproduction is sexual and flowering and fruiting apparently takes place throughout the year (Bradley and Gann 1999, p. 3).

Fire Ecology and Demography:
The fire ecology and demography of
Argythamnia blodgettii
have not been studied. Populations of
A. blodgettii
can be ephemeral (Hodges and Bradley 2006, p. 14).

Summary of Biological Status and Threats

The Act directs us to determine whether any species is an endangered species or a threatened species because of any one of five factors affecting its continued existence. In this section, we summarize the biological condition of each of the plant species and its resources, and the factors affecting them, to assess the species' overall viability and the risks to that viability.

Factor A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range

Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola,
and
Argythamnia blodgettii
have experienced substantial destruction, modification, and curtailment of their habitats and ranges (see Background, above). Specific threats to these plants included in this factor include habitat loss, fragmentation, and modification caused by development (
i.e.,
conversion to both urban and agricultural land uses) and inadequate fire management. Each of these threats and its specific effects on these plants are discussed in detail below.

Human Population Growth, Development, and Agricultural Conversion

The modification and destruction of the habitats that support
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola,
and
Argythamnia blodgettii
has been extreme in most areas of Miami-Dade and Monroe Counties, thereby reducing these plants' current ranges and abundance in Florida. The

pine rocklands community of south Florida, in which all four plants primarily occur, is critically imperiled locally and globally (FNAI 2012, p. 27). Destruction of pine rocklands and rockland hammocks has occurred since the beginning of the 1900s. Extensive land clearing for human population growth, development, and agriculture in Miami-Dade and Monroe Counties has altered, degraded, or destroyed thousands of acres of these once abundant ecosystems.

In Miami-Dade County, development and agriculture have reduced pine rocklands habitat by 90 percent in mainland south Florida. Pine rocklands habitat decreased from approximately 74,000 ha (183,000 ac) in the early 1900s, to only 8,140 ha (20,100 ac) in 1996 (Kernan and Bradley 1996, p. 2). The largest remaining intact pine rocklands (approximately 2,313 ha (5,716 ac)) is Long Pine Key in ENP. Outside of ENP, only about 1 percent of the pine rocklands on the Miami Rock Ridge have escaped clearing, and much of what is left are small remnants scattered throughout the Miami metropolitan area, isolated from other natural areas (Herndon 1998, p. 1).

Similarly, most of the pine rocklands in the Florida Keys (Monroe County) have been impacted (Hodges and Bradley 2006, p. 6). Pine rocklands historically covered 1,049 ha (2,592 ac) of Big Pine Key (Folk 1991, p. 188), the largest area of pine rocklands in the Florida Keys. Pine rocklands now cover approximately 582 ha (1,438 ac) of the island, a reduction of 56 percent (Bradley and Saha 2009, p. 3). There were no estimates of pine rocklands area on the other islands historically, but each contained much smaller amounts of the habitat than Big Pine Key. Remaining pine rocklands on Cudjoe Key cover 72 ha (178 ac), Little Pine has 53 ha (131 ac), No Name has 56 ha (138 ac), and Sugarloaf has 38 ha (94 ac). The total area of remaining pine rocklands in the Florida Keys is approximately 801 ha (1,979 ac). Currently, about 478 ha (1,181 ac) (82 percent) of the pine rocklands on Big Pine Key, and most of the pine rocklands on these other islands, are protected within the National Key Deer Refuge and properties owned by the Nature Conservancy, the State of Florida, and Monroe County (Bradley and Saha 2009, pp. 3-4). Based on the data presented above, the total remaining acreage of pine rocklands in Miami-Dade and Monroe Counties is now 8,981 ha (22,079 ac) (approximately 8,140 ha (20,100 ac) in Miami-Dade County, and 801 ha (1,979 ac) in the Florida Keys (Monroe County)).

The marl prairies that also support
Linum arenicola
have similarly been destroyed by the rapid development of Miami-Dade and Monroe Counties. At least some of the occurrences reported from this habitat may be the result of colonization that occurred after they were artificially dried-out due to local or regional drainage.

Likewise, habitat modification and destruction from residential and commercial development have severely impacted rockland hammocks, and coastal berm, that support
Argythamnia blodgettii.
Rockland hammocks were once abundant in Miami-Dade and Monroe Counties but are now considered imperiled locally and globally (FNAI 2010x, pp. 24-26). The tremendous development and agricultural pressures in south Florida have resulted in significant reductions of rockland hammock, which is also susceptible to fire, frost, hurricane damage, and groundwater reduction (Phillips 1940, p. 167; Snyder
et al.
1990, pp. 271-272; FNAI 2010, pp. 24-26).

Pine rocklands, rockland hammock, marl prairie, and coastal habitats on private land remain vulnerable to development, which could lead to the loss of populations of these four species. As noted earlier, all four plants have been impacted by development. The sites of Small's 1907 and 1911
L. arenicola
collections in Miami-Dade County are now agricultural fields (Kernan and Bradley 1996, p. 4). A pine rocklands site that supported
L. arenicola
on Vistalmar Street in Coral Gables (Miami-Dade County) was cleared and developed in 2005, as the Cocoplum housing development. A second pine rocklands site that supported
L. arenicola,
located on private land on Old Cutler Road, was developed into the Palmetto Bay Village Center.
L. arenicola
has not been observed at either site since they were developed. A former marl prairie site supporting a sizable population of
L. arenicola
near Old Cutler Road and Allapatah Drive (SW 112 Ave3.) in Miami-Dade County was extirpated when the site was developed in the 1990s (Bradley and van der Heiden 2013, pp. 6-12, 19). The Boca Chica Key population of
L. arenicola
was also likely lost due to development (Hodges and Bradley 2006, p. 48).

Bradley and Gann (1999, p. 6) list 12 populations of
Argythamnia blodgettii
in Miami-Dade County that were lost when the site that supported them was developed. An
A. blodgettii
population on Key West was likely lost due to the near complete urbanization of the island (Hodges and Bradley 2006, p. 43). Any development related to the Boy Scout camp on Big Munson Island is a potential threat to the largest population
A. blodgettii.

The largest
Linum arenicola
population in Miami-Dade County is located on property owned by the Miami-Dade County Homeless Trust. SOCSOUTH, a unified command of all four services of DOD, has entered into a 50-year agreement with Miami-Dade County to lease this 90-ac (36.4-ha) area, where they are building a permanent headquarters on approximately 28 ac (11.3 ha) (DOD 2009, p. 1). As stated above, the population of
L. arenicola
is spread across the site and was estimated at 74,000 plants in 2009 (Bradley 2009, p. 3). In consultation with the Service, the DOD developed a plan that avoided the majority of the population with accompanying protection and management of approximately 57,725 individuals of sand flax (about 78 percent of the estimated onsite population) (Service 2011, p. 13). The plan will manage 5.95 ha (14.7 ac) of habitat, though most of it is scraped, and only a small portion has a pine canopy (Van der Heiden and Johnson 2013, p. 2). An additional 1.3 ha (3.2 ac) is being managed and supports 13,184 individuals of sand flax (about 18 percent of the estimated onsite population) (Service 2011, p. 13).

Currently there are plans to develop 55 ha (137 ac) of the largest remaining parcel of pine rocklands habitat in Miami-Dade County, the Richmond pine rocklands, with a shopping center and residential construction (RAM 2014, p. 2). Bradley and Gann (1999, p. 4) called the 345-ha (853-ac) Richmond pine rocklands, “the largest and most important area of pine rockland in Miami-Dade County outside of Everglades National Park.” Populations of
Argythamnia blodgettii
and
Linum arenicola,
along with numerous federally listed species, occur there. The Miami-Dade County Department of Environmental Resources Management (DERM) has completed a management plan for portions of the Richmond pine rocklands under a grant from the Service and is leading the restoration and management of the Richmond pine rocklands (Bradley and Gann 1999, p. 4). The developer has proposed to enter into a habitat conservation plan in conjunction with their plans to develop their portion of the site and was required by Miami-Dade County Natural Forest Community (NFC) regulations to set aside and manage 15 ha (39 ac) of pine rocklands and 2 ha (4 ac) of rockland hammock. A second project that would result in the loss of pine rocklands habitat is also planned for the

Richmond pine rocklands. It includes expanding the Miami Zoo complex to develop an amusement park and large retail mall.

Approximately 25 percent of extant
Linum arenicola
occurrences (3 of 12 sites), and 44 percent of extant
Argythamnia blodgettii
occurrences (13 of 34 sites), are located on private land; no extant populations of
Chamaecrista lineata
var.
keyensis
or
Chamaesyce deltoidea
ssp.
serpyllum
are located entirely on private land. It is possible that the plants on private lands will be lost from most of these sites in the future with increased pressure from development and the other threats described below.
Argythamnia blodgettii
is the only one of the four plants species which occurs in ENP, where a population of over 2,000 plants is stable and prescribed fire and other management activities that benefit
A. blodgettii
are conducted on a regular basis.

Most pine rocklands and rockland hammock habitat is now limited to public conservation lands, where future development and habitat alteration are less likely than on private lands. However, public lands could be sold off (or leased) in the future and become more likely to be developed or altered in a way that negatively impacts the habitat. For example, at the SOCSOUTH site noted above (leased to DOD by Miami-Dade County), ongoing development of headquarters buildings SOCSOUTH has resulted in the loss of
L. arenicola
and pine rocklands habitat (Bradley and van der Heiden 2013, pp. 8-10). Construction of visitor facilities such as parking lots, roads, trails, and buildings can result in habitat loss on public lands that are set aside as preserves or parks.

Roadside populations of
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola,
and
Argythamnia blodgettii
are vulnerable to habitat loss and modification stemming from infrastructure projects such as road widening, and installation of underground cable, sewer, and water lines. The Lower Sugarloaf Key population of
Linum arenicola
was impacted by repaving of the road, which placed asphalt on top of and adjacent to the population (Hodges and Bradley 2006, p. 41).

Although no entire populations of
Chamaecrista lineata
var.
keyensis
or
Chamaesyce deltoidea
ssp.
serpyllum
have been extirpated by habitat loss due to development, the size and extent of these populations have been reduced on Big Pine Key (and surrounding islands for
Chamecrista lineata
var.
keyensis
). The total area of pine rockland on Big Pine Key has decreased by 56 percent from 1955 to the present (Bradley and Saha 2009, p. 3).

The human population within Miami-Dade County is currently greater than 2.4 million people, and is expected to grow to more than 4 million by 2060, an annual increase of roughly 30,000 people (Zwick and Carr 2006, p. 20). Overall, the human population in Monroe County is expected to increase from 79,589 to more than 92,287 people by 2060 (Zwick and Carr 2006, p. 21). All vacant land in the Florida Keys is projected to be developed by then, including lands currently inaccessible for development, such as islands not attached to the Overseas Highway (U.S. 1) (Zwick and Carr 2006, p. 14). However, in an effort to address the impact of development on federally listed species, Monroe County implemented a habitat conservation plan (HCP) for Big Pine and No Name Keys in 2006. In order to fulfill the HCP's mitigation requirements, the County has been actively acquiring parcels of high-quality pine rocklands, such as The Nature Conservancy's 20-acre Terrestris Tract on Big Pine Key, and managing them for conservation. Although the HCP has helped to limit the impact of development, land development pressure and habitat losses may resume when the HCP expires in 2023. If the HCP is not renewed, residential or commercial development could increase to pre-HCP levels.

While Miami-Dade and Monroe County both have developed a network of public conservation lands that include pine rocklands, rockland hammocks, marl prairies, and coastal habitats, much of the remaining habitat occurs on private lands as well as publicly owned lands not managed for conservation. Species occurrences and suitable habitat remaining on these lands are threatened by habitat loss and degradation, and threats are expected to accelerate with increased development. Further losses will seriously affect the four plant species' ability to persist in the wild and decrease the possibility of their recovery or recolonization.

Habitat Fragmentation

The remaining pine rocklands in the Miami metropolitan area are severely fragmented and isolated from each other by vast areas of development. Remaining pine rockland areas in the Florida Keys are fragmented and are located on small islands separated by ocean. Habitat fragmentation reduces the size of plant populations and increases spatial isolation of remnants. Barrios
et al.
(2011, p. 1062) investigated the effects of fragmentation on a pine rocklands plant,
Angadenia berteroi
(pineland golden trumpet), which is recognized by the State of Florida as threatened, and found that abundance and fragment size were positively related. Possley
et al.
(2008, p. 385) studied the effects of fragment size on species composition in south Florida pine rocklands, and found that plant species richness and fragment size were positively correlated (although some small fragments supported nearly as many species as the largest fragment). Composition of fragmented habitat typically differs from that of intact forests; as isolation and edge effects increase, there is increased abundance of disturbance-adapted species (weedy species, nonnative invasive species) and lower rates of pollination and propagule dispersal (Laurence and Bierregaard 1997, pp. 347-350; Noss and Csuti 1997, pp. 284-299). The degree to which fragmentation threatens the dispersal abilities of
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola,
and
Argythamnia blodgettii
is unknown. In the historical landscape, where pine rocklands occurred within a mosaic of wetlands, water may have acted as a dispersal vector for all pine rocklands seeds. In the current, fragmented landscape, this type of dispersal would no longer be possible for any of the Miami-Dade populations. While additional dispersal vectors may include animals and (in certain locations) mowing equipment, it is likely that fragmentation has effectively reduced these plants' ability to disperse and exchange genetic material.

While pollination research has not been conducted for
Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola,
and
Argythamnia blodgettii,
research regarding other species and ecosystems, including
Chamaecrista lineata
var.
keyensis
(discussed below), provides valuable information regarding potential effects of fragmentation on these plants. Effects of fragmentation on pollinators may include changes to the pollinator community as a result of limitation of pollinator-required resources (
e.g.,
reduced availability of rendezvous plants, nesting and roosting sites, and nectar/pollen); these changes may include changes to pollinator community composition, species abundance and diversity, and pollinator behavior (Rathcke and Jules 1993, pp. 273-275; Kremen and Ricketts 2000, p. 1227; Harris and Johnson 2004, pp. 30-33). As a result, plants in fragmented habitats may experience lower visitation rates, which in turn may result in

reduced seed production of the pollinated plant (which may lead to reduced seedling recruitment), reduced pollen dispersal, increased inbreeding, reduced genetic variability, and ultimately reduced population viability (Rathcke and Jules 1993, p. 275; Goverde
et al.
2002, pp. 297-298; Harris and Johnson 2004, pp. 33-34).

In addition to affecting pollination, fragmentation of natural habitats often alters other ecosystems' functions and disturbance regimes. Fragmentation results in an increased proportion of “edge” habitat, which in turn has a variety of effects, including changes in microclimate and community structure at various distances from the edge (Margules and Pressey 2000, p. 248), altered spatial distribution of fire (greater fire frequency in areas nearer the edge) (Cochrane 2001, pp. 1518-1519), and increased pressure from nonnative, invasive plants and animals that may out-compete or disturb native plant populations. Liu and Koptur (2003, p. 1184) reported decreases in
Chamaecrista lineata
var.
keyensis's
seed production in urban areas of Big Pine Key due to increased seed predation, compared with areas away from development.

The effects of fragmentation on fire go beyond edge effects and include reduced likelihood and extent of fires, and altered behavior and characteristics (
e.g.,
intensity) of those fires that do occur. Habitat fragmentation encourages the suppression of naturally occurring fires, and has prevented fire from moving across the landscape in a natural way, resulting in an increased amount of habitat suffering from these negative impacts. High fragmentation of small habitat patches within an urban matrix discourages the use of prescribed fire as well due to logistical difficulties (see “Fire Management,” below). Forest fragments in urban settings are also subject to increased likelihood of certain types of human-related disturbance, such as the dumping of trash (Chavez and Tynon 2000, p. 405). The many effects of habitat fragmentation may work in concert to threaten the local persistence of a species; when a species' range of occurrence is limited, threats to local persistence increase extinction risk.

Fire Management

One of the primary threats to
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola,
and
Argythamnia blodgettii
is habitat modification and degradation through inadequate fire management, which includes both the lack of prescribed fire and suppression of natural fires. Where the term “fire-suppressed” is used below, it describes degraded pine rocklands conditions resulting from a lack of adequate fire (natural or prescribed) in the landscape. Historically, frequent (approximately twice per decade), lightning-induced fires were a vital component in maintaining native vegetation and ecosystem functioning within south Florida pine rocklands (see Background, above). A period of just 10 years without fire may result in a marked decrease in the number of herbaceous species due to the effects of shading and litter accumulation (FNAI 2010, p. 63). Exclusion of fire for approximately 25 years will likely result in gradual hammock development over that time period, leaving a system that is very fire-resistant if additional pre-fire management (
e.g.,
mechanical hardwood removal) is not undertaken.

Today, natural fires are unlikely to occur or are likely to be suppressed in the remaining, highly fragmented pine rocklands habitat. The suppression of natural fires has reduced the size of the areas that burn, and habitat fragmentation has prevented fire from moving across the landscape in a natural way. Without fire, successional climax from pine rocklands to rockland hammock is rapid, and displacement of native species by invasive, nonnative plants often occurs. Understory plants such as
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola, and Argythamnia blodgettii
are shaded out by hardwoods and nonnatives alike. Shading may also be caused by a fire-suppressed pine canopy that has evaded the natural thinning effects that fire has on seedlings and smaller trees. Whether the dense canopy is composed of pine, hardwoods, nonnatives, or a combination, seed germination and establishment are inhibited in fire-suppressed habitat due to accumulated leaf litter, which also changes soil moisture and nutrient availability (Hiers
et al.
2007, pp. 811-812). This alteration to microhabitat can also inhibit seedling establishment as well as negatively influence flower and fruit production (Wendelberger and Maschinski 2009, pp. 849-851), thereby reducing sexual reproduction in fire-adapted species such as
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, L. arenicola,
and
A. blodgettii
(Geiger 2002, pp. 78-79, 81-83).

After an extended period of inadequate fire management in pine rocklands, it becomes necessary to control invading native hardwoods mechanically, as excess growth of native hardwoods would result in a hot fire, which can kill mature pines. Mechanical treatments cannot entirely replace fire because pine trees, understory shrubs, grasses, and herbs all contribute to an ever-increasing layer of leaf litter, covering herbs and preventing germination, as discussed above. Leaf litter will continue to accumulate even if hardwoods are removed mechanically. In addition, the ashes left by fires provide important post-fire nutrient cycling, which is not provided via mechanical removal.

Federal (Service, NPS), State (FDEP, FWC), and County land managers (Miami-Dade DERM), and nonprofit organizations (IRC) implement prescribed fire on public and private lands within the ranges of these four plants. While management of some County conservation lands includes regular burning, other lands remain severely fire-suppressed. Even in areas under active management, some portions are typically fire-suppressed.

Miami-Dade County:
Implementation of a prescribed fire program in Miami-Dade County has been hampered by a shortage of resources, as well as by logistical difficulties and public concern related to burning next to residential areas. Many homes have been built in a mosaic of pine rocklands, so the use of prescribed fire in many places has become complicated because of potential danger to structures and smoke generated from the burns. Nonprofit organizations such as IRC have similar difficulties in conducting prescribed burns due to difficulties with permitting and obtaining the necessary permissions as well as hazard insurance limitations (Gann 2013a, pers. comm.). Few private landowners have the means or desire to implement prescribed fire on their property, and doing so in a fragmented urban environment is logistically difficult and may be costly.

All occurrences of
Linum arenicola
and
Argythamnia blodgettii
in Miami-Dade County are affected by some degree of inadequate fire management of pine rocklands and marl prairie habitat, with the primary threat being the modification and loss of habitat due to an increase in shrub and hardwood dominance, eliminating suitable conditions for the four plants, and eventual succession to rockland hammock.

In Miami-Dade County,
Linum arenicola
occurred along the south edge of Bauer Drive on the northern border of a pine rockland owned by Miami-Dade County. The property is occupied by a communications tower, and is not a managed preserve. Kernan and Bradley (1996) reported eight plants. At the time

(1992 through 1996), the road shoulder was dominated by native grasses. Since then, native canopy hardwoods have invaded the site and eliminated the sunny conditions required by
L. arenicola.
It has not been seen since, despite multiple surveys between 1997 and 2012, and is considered to be extirpated.
L. arenicola
was discovered at Camp Owaissa Bauer by George N. Avery in 1983. Since that time, the pine rocklands habitat where he found the plants in the park suffered extremely heavy hardwood recruitment due to fire suppression. Despite recent hardwood control and reintroduction of fire, no plants have been relocated. At the Martinez pineland, a population of
L. arenicola
in a marl prairie that became overgrown due to lack of fire has not been observed since 2011. Plants may reappear at this site if prescribed fire is implemented and viable seeds remain in the soil (Bradley and van der Heiden 2013, pp. 8-11). Bradley and Gann (1999, pp. 71-72) suggested that the lack of fires in most forest fragments in Miami-Dade County during the last century may be one of the reasons why
L. arenicola
occurs primarily in disturbed areas.

Monroe County (Florida Keys):
Fire management of pine rocklands of the lower Florida Keys, most of which are within NKDR, is hampered by a shortage of resources, technical challenges, and expense of conducting prescribed fire in a matrix of public and private ownership. Residential and commercial properties are embedded within or in close proximity to pine rocklands habitat (Snyder
et al.
2005, p. 2; C. Anderson 2012a, pers. comm.). As a result, hand or mechanical vegetation management may be necessary at select locations on Big Pine Key (Emmel
et al.
1995, p. 11; Minno 2009, pers. comm.; Service 2010, pp. 1-68) to maintain or restore pine rocklands. Mechanical treatments may be less beneficial than fire because they do not quickly convert debris to nutrients, and remaining leaf litter may suppress seedling development; fire has also been found to stimulate seedling germination (C. Anderson 2010, pers. comm.). Because mechanical treatments may not provide the same ecological benefits as fire, NKDR continues to focus efforts on conducting prescribed fire where possible (C. Anderson 2012a, pers. comm.). However, the majority of pine rocklands within NKDR are several years behind the ideal fire return interval (5-7 years) suggested for this ecosystem (Synder
et al.
2005, p. 2; Bradley and Saha 2011, pp. 1-16). Tree ring and sediment data show that pine rocklands in the lower Keys have burned at least every 5 years and sometimes up to three times per decade historically (Albritton 2009, p. 123; Horn
et al.
2013, pp. 1-67; Harley 2012, pp. 1-246). From 1985 to 1992, prescribed burns were conducted in the NKDR mainly for fuel reduction. There was no prescribed burning by Service staff in the NKDR from 1992-1997, in part because not enough was known about the ecological effects of prescribed fire in this system (Snyder
et al.
1990, p. 2).

All occurrences of
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum, Linum arenicola,
and
Argythamnia blodgettii
in the Florida Keys are affected by some degree of inadequate fire management of pine rocklands habitat, with the primary threat being the modification and loss of habitat due to an increase in shrub and hardwood dominance, eliminating suitable conditions for the four plants, and eventual succession to rockland hammock.

Prescribed fire management over the past decade has not been sufficient to reverse long-term declines in
Chamaecrista lineata
var.
keyensis, Chamaesyce deltoidea
ssp.
serpyllum,
or
Linum arenicola
on Big Pine Key. Prescribed fire activity on Big Pine Key and adjacent islands within NKDR appears to be insufficient to prevent loss of pine rocklands habitat (Carlson
et al.
1993, p. 914; Bergh and Wisby 1996, pp. 1-2; O'Brien 1998, p. 209; Bradley and Saha 2009, pp. 28-29; Bradley
et al.
2011, pp. 1-16). As a result, many of the pine rocklands across NKDR are being compromised by succession to rockland hammock (Bradley and Saha 2009, pp. 28-29; Bradley
et al.
2011, pp. 1-16).

Conservation Efforts To Reduce the Present or Threatened Destruction, Modification, or Curtailment of Habitat or Range

Miami-Dade County Environmentally Endangered Lands (EEL) Covenant Program:
In 1979, Miami-Dade County enacted the Environmentally Endangered Lands (EEL) Covenant Program, which reduces taxes for private landowners of natural forest communities (NFCs; pine rocklands and tropical hardwood hammocks) who agree not to develop their property and manage it for a period of 10 years, with the option to renew for additional 10-year periods (Service 1999, p. 3-177). Although these temporary conservation easements provide valuable protection for their duration, they are not considered under Factor D, below, because they are voluntary agreements and not regulatory in nature. Miami-Dade County currently has approximately 59 pine rocklands properties enrolled in this program, preserving 69.4 ha (172 ac) of pine rocklands habitat (Johnson 2012, pers. comm.). The program also has approximately 21 rockland hammocks properties enrolled in this program, preserving 20.64 ha (51 ac) of rockland hammock habitat (Joyner 2013b, pers. comm.). The vast majority of these properties are small, and many are in need of habitat management such as prescribed fire and removal of nonnative, invasive plants. Thus, while EEL covenant lands have the potential to provide valuable habitat for these plants and reduce threats in the near term, the actual effect of these conservation lands is largely determined by whether individual land owners follow prescribed EEL management plans and NFC regulations (see “Local” under Factor D discussion, below).

Fee Title Properties:
In 1990, Miami-Dade County voters approved a 2-year property tax to fund the acquisition, protection, and maintenance of natural areas by the EEL Program. The EEL Program purchases and manages natural lands for preservation. Land uses deemed incompatible with the protection of the natural resources are prohibited by current regulations; however, the County Commission ultimately controls what may happen with any County property, and land use changes may occur over time (Gil 2013b, pers. comm.). To date, the Miami-Dade County EEL Program has acquired a total of approximately 313 ha (775 ac) of pine rocklands, and 95 ha (236 ac) of rockland hammocks (Guerra 2015, pers. comm.; Gil 2013b, pers. comm.). The EEL Program also manages approximately 314 ha (777 ac) of pine rocklands, and 639 ha (1,578 ac) of tropical hardwood and rockland hammocks owned by the Miami-Dade County Parks, Recreation and Open Spaces Department, including some of the largest remaining areas of pine rocklands habitat on the Miami Rock Ridge outside of ENP (
e.g.,
Larry and Penny Thompson Park, Zoo Miami pinelands, Navy Wells Pineland Preserve), and some of the largest remaining areas of tropical hardwood and rockland hammocks (
e.g.,
Matheson Hammock Park, Castellow Hammock Park, Deering Estate Park and Preserves).

Conservation efforts in Miami's EEL Preserves have been underway for many years. In Miami-Dade County, conservation lands are and have been monitored by FTBG and IRC, in coordination with the EEL Program, to assess habitat status and determine any

changes that may pose a threat to or alter the abundance of these species. Impacts to habitat (
e.g.,
canopy) via nonnative species and natural stochastic events are monitored and actively managed in areas where the taxon is known to occur. These programs are long-term and ongoing in Miami-Dade County; however, programs are limited by the availability of annual funding.

Since 2005, the Service has funded IRC to facilitate restoration and management of privately owned pine rocklands habitats in Miami-Dade County. These programs included prescribed burns, nonnative plant control, light debris removal, hardwood management, reintroduction of pines where needed, and development of management plans. One of these programs, called the Pine Rockland Initiative, includes 10-year cooperative agreements between participating landowners and the Service/IRC to ensure restored areas will be managed appropriately during that time. Although most of these objectives have been achieved, IRC has not been able to conduct the desired prescribed burns, due to logistical difficulties as discussed earlier (see “Fire Management,” above).

Connect to Protect Program:
Fairchild Tropical Botanic Garden (FTBG), with the support of various Federal, State, and local agencies and nonprofit organizations, has established the “Connect to Protect Network.” The objective of this program is to encourage widespread participation of citizens to create corridors of healthy pine roc

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2015-24291. Public record. Not legal advice.