Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for the Plants Ayenia limitaris (Texas Ayenia) and Ambrosia cheiranthifolia (South Texas Ambrosia)

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AC01

Endangered and Threatened Wildlife and Plants; Determination of

Endangered Status for the Plants Ayenia limitaris (Texas Ayenia) and

Ambrosia cheiranthifolia (South Texas Ambrosia)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: The Fish and Wildlife Service (Service) determines Ayenia

limitaris (Texas ayenia) and Ambrosia cheiranthifolia (South Texas

ambrosia) to be endangered species under the authority of the

Endangered Species Act (Act) of 1973, as amended. Texas ayenia is known

from a single population in Hidalgo County, Texas. South Texas ambrosia

has been verified recently from eight populations, four in Nueces

County, three in Kleberg County, and one overlapping both counties in

Texas. These species are threatened by habitat destruction and

fragmentation through alteration and conversion of native plant

communities to commercial uses; displacement by invasive nonnative

grasses; and low population numbers. This action will implement Federal

protection provided by the Act for Texas ayenia and South Texas

ambrosia. Critical habitat is not being designated.

EFFECTIVE DATE: September 23, 1994.

ADDRESSES: The complete file for this rule is available for inspection,

by appointment, during normal business hours at the Corpus Christi

Ecological Services Field Office, U.S. Fish and Wildlife Service, c/o

Texas A&M University at Corpus Christi, Campus Box 338, 6300 Ocean

Drive, Corpus Christi, Texas 78412.

FOR FURTHER INFORMATION CONTACT: Angela Brooks, at the above address

(telephone 512/994-9005; facsimile 512/994-8262).

SUPPLEMENTARY INFORMATION:

Background

Texas ayenia, a member of the cacao family, was first collected in

Hidalgo County, Texas, by C.G. Pringle in 1888, and was named

Nephropetalum pringlei by B.L. Robinson and J.M. Greenman in 1896. In

1960, Carmen Cristobal revised the genus Ayenia and described Ayenia

limitaris as a new species. The previously described Nephropetalum

pringlei was not mentioned in the revision. Prior to Cristobal's

description of Ayenia limitaris in 1960, South Texas specimens of this

species had been identified as A. berlandieri, a species of tropical

Mexico. In 1986, Laurence Dorr and Lisa Barnett transferred

Nephropetalum pringlei to the genus Ayenia and reduced it to synonymy

with Ayenia limitaris.

Texas ayenia is a pubescent subshrub approximately 60-150

centimeters (cm) (2-5 feet (ft)) tall, with alternate, simple leaves.

The cordate-based leaves are approximately 8 cm (3 inches (in)) long

and 3.5 cm (1.4 in) wide. The inflorescences are axillary, up to 4 per

node, with each inflorescence supporting two or more perfect flowers.

Flower color has been reported as green, pink, or cream. The fruit is a

5-celled, pubescent capsule approximately 8 millimeters (mm) (0.3 in)

long, with short, curved prickles (Damude and Poole 1990).

Texas ayenia occurs at low elevations in dense subtropical woodland

communities. Previous collectors have found the plant in openings

within chaparral and along the edges of thickets (Correll and Johnston

1979). The present site is a Texas Ebony-Anacua (Pithecellobium ebano-

Ehretia anacua) plant community located within the Arroyo Colorado

drainage. This area was once an active floodplain; however, the effect

of past flooding on Texas ayenia is unknown.

The Texas Ebony-Anacua plant community, which occurs on well

drained, but heavy soils on riparian terraces, once covered much of the

Rio Grande delta (Diamond 1990). Canopy cover is close to 95 percent in

this climax community type (Damude and Poole 1990). Associated species

include la coma (Bumelia celastrina), brasil (Condalia hookeri),

granjeno (Celtis pallida), and snake-eyes (Phaulothamnus spinescens).

The Texas Ebony-Anacua community grades into the Texas Ebony-Snake-eyes

community in the drier portions of the woodland habitat (Diamond 1990).

Both plant communities have been reduced to discontinuous fragments,

often surrounded by agricultural fields, pastures, or urban

development, and now cover less than 5 percent of their original area

(Jahrsdoerfer and Leslie 1988).

Texas ayenia occurred historically in Cameron and Hidalgo Counties

in the United States, and the states of Coahuila, Nuevo Leon, and

Tamaulipas in Mexico. The only recent collection in Mexico was from a

Tamaulipan population in 1981; however, the present status of this

population is unknown (Damude and Poole 1990). Texas ayenia has not

been relocated at any of the historic Cameron County locations since

the early 1960s. The status report by Damude and Poole (1990) noted a

1988 observation of six spindly plants at the Hidalgo County site, and

the following year only one individual was observed.

Searches were undertaken in 1990 and 1991 by a number of personnel

from the Service and Texas Parks and Wildlife Department, but no plants

were found. In 1992, Service personnel and Jim Everitt of the U.S.

Department of Agriculture located one plant at the Hidalgo County site.

In 1994, Joe Ideker (Native Plant Project, McAllen, Texas, pers.comm.

1994) located 20 additional plants at this site. This site, on private

property, is the only one recently verified for the species.

South Texas ambrosia was first collected in San Fernando,

Tamaulipas, Mexico, by Luis Berlandier in 1835, and was named Ambrosia

cheiranthifolia by A. Gray in 1859. The first United States collection

was made in 1932 by Robert Runyon from an area near Barreda (now

Russelltown) in Cameron County, Texas (Turner 1983).

South Texas ambrosia, a member of the aster family, is a

herbaceous, erect, silvery to grayish-green, rhizomatous perennial

plant, 10-30 cm (0.3-1.0 ft) tall. Its simple leaves are usually

opposite on the lower portion of the plant and alternate above. The

staminate flower heads are arranged in inconspicuous terminal racemes

5-10 cm (2-4 in) long. The pistillate flower heads are in small

clusters in the leaf axils just below the staminate racemes (Turner

1983). Due to its rhizomatous growth, a single plant may be represented

by hundreds of clonal stems.

South Texas ambrosia grows at low elevations in open clay-loam to

sandy-loam prairies and savannas. Much of the original native habitat

for South Texas ambrosia has been converted to agricultural fields,

improved pastures, or urban areas. Many savanna areas have been cleared

and planted to nonnative grasses, such as buffelgrass (Cenchrus

ciliaris), which outcompete and eventually displace much of the native

vegetation. Other potential prairie habitat may now be invaded by

thorny shrub and tree species as a result of fire suppression or

overgrazing. South Texas ambrosia does not appear to survive intensive

plowing, blading, or disking; however, some lesser soil disturbance may

enhance its growth. Associated native grasses found at the existing

sites include Texas grama (Bouteloua rigidiseta), buffalo grass

(Buchloe dactyloides), Texas speargrass (Stipa leucotricha), and tobosa

(Hilaria mutica). Invading nonnative grasses found at the sites include

buffelgrass, King Ranch bluestem (Bothriochloa ischaemum var.

songarica), bermuda grass (Cynodon dactylon), and St. Augustine grass

(Stenotaphrum secundatum) (U.S. Fish and Wildlife Service 1988).

Associated native woody species found scattered throughout the existing

sites include mesquite (Prosopis glandulosa), huisache (Acacia

smallii), huisachillo (Acacia schaffneri), brasil (Condalia hookeri),

granjeno (Celtis pallida), and lotebush (Ziziphus obtusifolia).

Historically, South Texas ambrosia occurred in Cameron, Jim Wells,

Kleberg, and Nueces counties in South Texas, and the state of

Tamaulipas in Mexico. The current status of any Mexican populations is

unknown. The historic populations in Cameron and Jim Wells counties

have not been relocated. Only one location noted in the status report

(Turner 1983) is known to be still extant. Three populations, two in

Nueces County, and one in Kleberg County, were discovered by Ruth

O'Brien (Texas A&M University at Corpus Christi, pers. comm. 1993).

Three Nueces County populations were discovered in 1992 and 1993 by

William Carr (Texas Parks and Wildlife Department, pers. comm. 1993).

The extant populations occur on private land, highway and railroad

rights-of-way, and the Kingsville Naval Air Station. Four historic

locations for South Texas ambrosia, one extirpated and three extant,

also support the endangered slender rush-pea (Hoffmannseggia tenella),

which was federally listed (50 FR 45624; November 1, 1985) because of

threats similar to those affecting South Texas ambrosia. One known

location for South Texas ambrosia also supports the endangered black

lace cactus (Echinocereus reichenbachii var. albertii), which was

federally listed (44 FR 61918; October 26, 1979) because of habitat

destruction and collecting threats.

Federal action on these species began as a result of section 12 of

the Endangered Species Act (16 U.S.C. 1531 et seq.), which directed the

Secretary of the Smithsonian Institution to prepare a report on those

plants considered to be endangered, threatened, or extinct in the

United States. This report, designated as House Document No. 94-51, was

presented to Congress on January 9, 1975. On July 1, 1975, the Service

published a notice in the Federal Register (40 FR 27823) accepting the

Smithsonian report as a petition within the context of section 4(c)(2)

of the Act, now section 4(b)(3)(A), and giving notice of its intention

to review the status of the plants named therein. Ambrosia

cheiranthifolia was included as endangered, and Ayenia limitaris, then

under the name Nephropetalum pringlei, was included as extinct in the

Smithsonian report and Service notice.

On June 16, 1976, the Service published a proposed rule in the

Federal Register (41 FR 24523) to determine approximately 1,700

vascular plant species to be endangered. Ambrosia cheiranthifolia was

included in the June 16, 1976, proposal. The 1978 amendments to the Act

required that all proposals over two years old be withdrawn, although a

one year grace period was given to proposals already over two years

old. In the December 10, 1979, Federal Register (44 FR 70796), the

Service published a notice withdrawing the June 16, 1976 proposal,

along with four other proposals that had expired.

A list of plants under review for listing as endangered or

threatened species was published in the December 15, 1980, Federal

Register (45 FR 82479). Ambrosia cheiranthifolia was included in

Category 2 of the list and Nephropetalum pringlei was included in

Category 1*. Category 2 species are those for which there is some

evidence of vulnerability, but for which there are insufficient data to

support listing proposals at the time. Category 1 species are those for

which the Service has on file substantial data on biological

vulnerability and threats to support the preparation of listing

proposals. Category 1* species are also those whose status in the

recent past is known to support listing, but that may have already

become extinct.

Section 4(b)(3)(B) of the Act requires the Secretary to make

certain findings on pending petitions within one year of their receipt.

Section 2(b)(1) of the 1982 amendments further requires that all

petitions pending on October 13, 1982, be treated as having been newly

submitted on that date. Because the 1975 Smithsonian report was

accepted as a petition, all of the plants contained therein, including

Nephropetalum pringlei (=Ayenia limitaris) and Ambrosia

cheiranthifolia, were treated as being newly petitioned on October 13,

1982. In each year from 1983 through 1992, the Service found that the

petitioned action was warranted, but listings of Ayenia limitaris and

Ambrosia cheiranthifolia were precluded by other listing actions of

higher priority in accordance with section 4(b)(3)(B)(iii) of the Act.

A status report on South Texas ambrosia was completed May 20, 1983

(Turner 1983). This report provided sufficient biological information

to justify proposing to list South Texas ambrosia as endangered.

Notices revising the 1980 list of plants under review for listing

as endangered or threatened species were published in the Federal

Register on September 27, 1985 (50 FR 39526) and February 21, 1990 (55

FR 6184). Nephropetalum pringlei (=Ayenia limitaris) was included in

Category 2 and Ambrosia cheiranthifolia was included in Category 1 of

these notices.

A status report on Texas ayenia was completed December 1, 1990

(Damude and Poole 1990). This report provided sufficient biological

information to justify proposing to list Texas ayenia as endangered.

The proposed rule to list Texas ayenia and South Texas ambrosia as

endangered was published in the Federal Register on August 5, 1993 (58

FR 41696). Publication of that proposed rule constituted the final one-

year finding for these species.

Summary of Comments and Recommendations

In the August 5, 1993, proposed rule and associated notifications,

all interested parties were requested to submit factual reports or

information that might contribute to the development of a final rule.

Appropriate Federal and State agencies, county governments, scientific

organizations, and other interested parties were contacted and

requested to comment. Newspaper notices, which invited general public

comment, were published in the Monitor (McAllen, Texas) and the Corpus

Christi Caller Times (Corpus Christi, Texas) on August 20, 1993, and

August 17, 1993, respectively. Three comments were received. Two

commenters supported the listing; one commenter was neutral. Issues

raised by commenters are discussed below.

Issue 1--The proposed rule fails to note industrial development as

one of the major causes of habitat loss for rare plants.

Service Response--The Service has included industrial development

as a threat in this final rule.

Issue 2--From the proposed rule discussion of the taxonomic history

of Texas ayenia it is unclear why the correct scientific name is not

Ayenia pringlei because Nephropetalum pringlei is an earlier name than

Ayenia limitaris.

Service Response--Dorr and Barnett (1986) concluded that the

correct placement of this species was within the genus Ayenia. However,

the specific epithet pringlei had already been used for another species

in Ayenia. So, although the name Nephropetalum pringlei is earlier than

Ayenia limitaris, the use of pringlei as the specific epithet would

create two species with the same name, which is not allowed by the

rules of botanical nomenclature.

Issue 3--Records for South Texas ambrosia indicate 25 occurrences,

with 17 of them extant. Records show 5 occurrences in Nueces County, 11

in Kleberg County, and 1 occurrence overlapping in both counties.

Service Response--The discrepancy between the number of occurrences

given in the comment letter and the number of populations reported in

the proposed rule is due to the Service considering several of the

occurrences to be close enough together to be part of a single

population.

Issue 4--One commenter noted that if individuals of either species

were present on floodways the plants would not obstruct flows,

therefore, vegetation maintenance in the floodways would not affect the

plants.

Service Response--While individual plants may not obstruct flood

flows, the densely wooded community in which Texas ayenia occurs would.

Should this densely wooded community be present, or new areas of

appropriate habitat be added to the floodway system, Federal agencies

would need to determine the species' absence before conducting floodway

vegetation maintenance.

Issue 5--One commenter provided an assessment of the threats of

habitat destruction, fragmentation, and loss of genetic variability on

both species.

Service Response--The Service appreciates this information.

Issue 6--One commenter offered to coordinate with the Service to

protect the species and their habitats.

Service Response--The Service appreciates the need to cooperate and

coordinate with Federal, state, and local agencies, private

organizations, and citizens to protect and recover these species.

Summary of Factors Affecting the Species

After a thorough review and consideration of all information

available, the Service has determined that Texas ayenia and South Texas

ambrosia should be classified as endangered species. Procedures found

at section 4(a)(1) of the Act and regulations (50 CFR part 424)

promulgated to implement the listing provisions of the Act were

followed. A species may be determined to be an endangered or threatened

species due to one or more of the five factors described in section

4(a)(1). These factors and their application to Ayenia limitaris

Cristobal (Texas ayenia) and Ambrosia cheiranthifolia Gray (South Texas

ambrosia) are as follows:

A. The present or threatened destruction, modification, or

curtailment of its habitat or range. Habitat destruction is the primary

threat to Texas ayenia and South Texas ambrosia. The past and current

practices of converting native South Texas brush and woodlands to

agricultural fields, improved pastures, and urban areas, or clearing

brush and woodlands for urban water development, industrial

development, or flood control have destroyed 95 percent of this native

vegetation (Jahrsdoerfer and Leslie 1988). Most native Texas Gulf Coast

prairies have been converted to agricultural fields or improved

pastures. The amount of conversion of these plant communities in Mexico

is similar though not quantified. The remaining remnant native prairie,

brush, and woodland tracts are often surrounded by agricultural fields,

pastures, or urban development. These modified habitats pose potential

threats to the native areas through agricultural chemical drift from

aerial spraying; chemical runoff following rains; invasion of nonnative

grasses such as buffelgrass, guineagrass (Panicum maximum), King Ranch

bluestem, and Angleton bluestem (Dichanthium aristatum); and trampling

and possible collection pressures due to easy accessibility from nearby

urban areas. The few remaining populations of the species are

vulnerable to extinction if any of their remaining habitat is modified.

Even roadside remnants of native vegetation in South Texas are

often bladed, or plowed and seeded with exotic grasses such as

buffelgrass and King Ranch bluestem. Herbicides are often used to

control vegetation around signs, guard rails, and bridge abutments, and

to kill shrubby vegetation encroaching on the right-of-way. Due to the

rarity of Texas ayenia and South Texas ambrosia, the likelihood they

will be directly impacted by roadway maintenance is small, but almost

any impact could lead to extinction of either species.

B. Overutilization for commercial, recreational, scientific, or

educational purposes. No commercial trade is known for either of these

species; however, the potential exists for vandalism and collection.

Listing these species, with the resulting publicity, will highlight

their rarity and may increase their attractiveness to some collectors.

Excessive recreational or scientific use is not known or anticipated

for either species.

C. Disease or predation. Although the Texas ayenia population has

shown no evidence of disease or predation, Cristobal (1960) notes the

floral buds of Ayenia species are often deformed by Hymenopteran

larvae. Cristobal also notes Ayenia fruits can be deformed by Dipteran

larvae thus inhibiting seed release. No evidence of grazing or browsing

has been observed for Texas ayenia.

No threats of disease or predation are known for South Texas

ambrosia; however, damage to stems and rhizomes is possible in

situations of severe trampling or grazing.

D. The inadequacy of existing regulatory mechanisms. Presently,

neither species is protected by Federal or State law. Listing under the

Act would provide protection for these species.

E. Other natural or manmade factors affecting its continued

existence. With only one known verified population, Texas ayenia may

have low genetic variability, which could limit its ability to adapt to

environmental changes. It is unknown whether past flooding created or

maintained habitat for Texas ayenia. However, since the present

population occurs within a previously active drainage of the Arroyo

Colorado (Damude and Poole 1990), a flood could negatively impact the

species. Observers have noted that the population declined during the

recent drought in the Lower Rio Grande Valley (J. Everitt, U.S.

Department of Agriculture, pers. comm. 1992). The extreme rarity of

this species makes it vulnerable to extinction from any number of

chance events.

South Texas ambrosia may also be vulnerable to extinction due to

lowered genetic variability. Populations are clonal, so despite having

many stems, the populations may actually represent very few genetically

different individuals. It has been noted that species like South Texas

ambrosia that were once more widespread, but are now reduced to low

numbers, may be more vulnerable to the detrimental effects of lowered

genetic diversity than species that were always rare (Huenneke 1991).

The Service has carefully assessed the best scientific and

commercial information available regarding the past, present, and

future threats faced by these species in determining to make this rule

final. Based on this evaluation, the preferred action is to list Texas

ayenia and South Texas ambrosia as endangered. The status of endangered

is appropriate because of these species' limited distribution, low

population numbers, and imminent threats of habitat destruction.

Critical Habitat

Critical habitat is defined in section 3 of the Act as--(i) The

specific areas within the geographic area occupied by a species, at the

time it is listed in accordance with the Act, on which are found those

physical features (I) Essential to the conservation of the species and

(II) that may require special management consideration or protection

and; (ii) specific areas outside the geographic areas occupied by a

species at the time it is listed, upon a determination that such areas

are essential for the conservation of the species. ``Conservation''

means the use of all methods and procedures needed to bring the species

to the point at which listing under the Act is no longer necessary.

Section 4(a)(3) of the Act, as amended, and implementing

regulations (50 CFR 424.12) require that, to the maximum extent prudent

and determinable, the Secretary designate critical habitat at the time

a species is determined to be endangered or threatened. The Service

finds that designation of critical habitat is not prudent for Texas

ayenia and South Texas ambrosia at this time. Service regulations (50

CFR 424.12(a)(1)) state that designation of critical habitat is not

prudent when one or both of the following situations exist--(1) The

species is threatened by taking or other human activity, and

identification of critical habitat can be expected to increase the

degree of threat to the species, or (2) such designation of critical

habitat would not be beneficial to the species.

As discussed under Factor B in the ``Summary of Factors Affecting

the Species,'' Texas ayenia and South Texas ambrosia are potentially

threatened by taking or vandalism. These activities are difficult to

prevent and only regulated by the Act with respect to plants in cases

of (1) Removal and reduction to possession of listed plants from lands

under Federal jurisdiction, or their malicious damage or destruction on

such lands; and (2) removal, cutting, digging up, or damaging or

destroying in knowing violation of any State law or regulation,

including State criminal trespass law. Such provisions are difficult to

enforce, and publication of critical habitat descriptions and maps

would make Texas ayenia and South Texas ambrosia more vulnerable to

collecting or vandalism and increase enforcement problems. All involved

parties and principal landowners have been notified of the location and

importance of protecting these species' habitat. Protection of these

species' habitat will be addressed through the recovery process and

through section 7 consultation. Therefore, it would not now be prudent

to determine critical habitat for Texas ayenia and South Texas

ambrosia.

Available Conservation Measures

Conservation measures provided to species listed as endangered or

threatened under the Endangered Species Act include recognition,

recovery actions, requirements for Federal protection, and prohibitions

against certain practices. Recognition through listing encourages and

results in conservation actions by Federal, State, and private

agencies, groups, and individuals. The Act provides for possible land

acquisition and cooperation with the States and requires that recovery

actions be carried out for all listed species. The protection required

of Federal agencies and the prohibitions against certain activities

involving listed plants are discussed, in part, below.

Section 7(a) of the Act, as amended, requires Federal agencies to

evaluate their actions with respect to any species that is proposed or

listed as endangered or threatened and with respect to its critical

habitat if any is being designated. Regulations implementing this

interagency cooperation provision of the Act are codified at 50 CFR

part 402. Section 7(a)(2) requires Federal agencies to ensure that

activities they authorize, fund, or carry out are not likely to

jeopardize the continued existence of a listed species or to destroy or

adversely modify its critical habitat. If a Federal action may affect a

listed species or its critical habitat, the responsible Federal agency

must enter into formal consultation with the Service.

Some Federal actions that may affect Texas ayenia or South Texas

ambrosia include brush clearing for flood control by the International

Boundary and Water Commission, management recommendations to landowners

by the Soil Conservation Service for activities funded by the

Agricultural Stabilization and Conservation Service, and agricultural

pesticide registration by the Environmental Protection Agency.

Additionally, a population of South Texas ambrosia occurs on Kingsville

Naval Air Station and may be affected by maintenance or construction

activities at this facility.

The Act and its implementing regulations set forth a series of

general prohibitions and exceptions that apply to all endangered

plants. All prohibitions of section 9(a)(2) of the Act, implemented by

50 CFR 17.61, apply. These prohibitions, in part, make it illegal for

any person subject to the jurisdiction of the United States to import

or export, transport in interstate or foreign commerce in the course of

a commercial activity, sell or offer for sale in interstate or foreign

commerce, or to remove and reduce these species to possession from

areas under Federal jurisdiction. In addition, for plants listed as

endangered, the Act prohibits malicious damage or destruction on

Federal lands and removal, cutting, digging up, or damaging or

destroying of such plants in knowing violation of any State law or

regulation, including State criminal trespass law. Certain exceptions

to the prohibitions apply to agents of the Service and State

conservation agencies.

The Act and 50 CFR 17.62 and 17.63 also provide for the issuance of

permits to carry out otherwise prohibited activities involving

endangered plants under certain circumstances. Such permits are

available for scientific purposes and to enhance the propagation and

survival of the species. It is anticipated that few trade permits would

ever be sought or issued because the species are not in cultivation or

common in the wild. Requests for copies of the regulations regarding

listed species and inquiries regarding prohibitions and permits may be

addressed to U.S. Fish and Wildlife Service, Division of Endangered

Species/Permits, P.O. Box 1306, Albuquerque, New Mexico 87103

(telephone 505/766-3972; facsimile 505/766-8063).

National Environmental Policy Act

The Fish and Wildlife Service has determined that Environmental

Assessments and Environmental Impact Statements, as defined under the

authority of the National Environmental Policy Act of 1969, need not be

prepared in connection with regulations adopted pursuant to section

4(a) of the Endangered Species Act of 1973, as amended. A notice

outlining the Service's reasons for this determination was published in

the Federal Register on October 25, 1983 (48 FR 49244).

References Cited

Cristobal, C.L. 1960. Revision del genero Ayenia L. (Sterculiaceae).

Opera Lilloana 4:1-230.

Damude, N., and J. Poole. 1990. Status report on Avenia limitaris.

U.S. Fish and Wildlife Service, Albuquerque, New Mexico.

Diamond, D. 1990. Plant communities of Texas (series level). Texas

Parks and Wildlife Department, Austin, Texas.

Dorr, L.J., and L.C. Barnett. 1986. The identity of Nephropetalum

(Sterculiaceae). Taxon 35(1):163-164.

Huenneke, L.F. 1991. Ecological implications of genetic variation in

plant populations. In D. Falk and K. Holsinger, eds. Genetics and

Conservation of Rare Plants. Oxford University Press, New York.

Jahrsdoerfer, S.E., and D.M. Leslie, Jr. 1988. Tamaulipan brushland

of the Lower Rio Grande Valley of South Texas: description, human

impacts, and management options. U.S. Fish and Wildlife Service,

Biol. Rep. 88(36). 63 pp.

Turner, B.L. 1983. Status report on Ambrosia cheiranthifolia. U.S.

Fish and Wildlife Service, Albuquerque, New Mexico.

U.S. Fish and Wildlife Service. 1988. Slender rush-pea

(Hoffmannseggia tenella) recovery plan. U.S. Fish and Wildlife

Service, Albuquerque, New Mexico. 38 pp.

Author

The primary author of this final rule is Angela Brooks (see

ADDRESSES section).

List of Subjects in 50 CFR Part 17

Endangered and threatened species, Exports, Imports, Reporting and

recordkeeping requirements, and Transportation.

Regulation Promulgation

Accordingly, part 17, subchapter B of chapter I, title 50 of the

Code of Federal Regulations, is amended as set forth below:

PART 17--[AMENDED]

1. The authority citation for part 17 continues to read as follows:

Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C.

4201-4245; Pub. L. 99-625, 100 Stat. 3500; unless otherwise noted.

2. Section 17.12(h) is amended by adding the following, in

alphabetical order under the plant families indicated, to the List of

Endangered and Threatened Plants to read as follows:

Sec. 17.12 Endangered and threatened plants.

* * * * *

(h) * * *

----------------------------------------------------------------------------------------------------------------

Species

---------------------------------------- Historic range Status When listed Critical Special

Scientific name Common name habitat rules

----------------------------------------------------------------------------------------------------------------

* * * * * * *

Asteraceae--Aster

family:

* * * * * * *

Ambrosia South Texas U.S.A. (TX), E 547 NA NA

cheiranthifoli ambrosia. Mexico.

a.

* * * * * * *

Sterculiaceae--Caca

o family:

Ayenia Texas Ayenia...... U.S.A. (TX), E 547 NA NA

limitaris. Mexico.

* * * * * * *

----------------------------------------------------------------------------------------------------------------

Dated: July 11, 1994.

Mollie H. Beattie,

Director, Fish and Wildlife Service.

[FR Doc. 94-20789 Filed 8-23-94; 8:45 am]

BILLING CODE 4310-55-P