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CPC National Collection Plant Profile

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Kathy Rice

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CPC National Collection Plant Profile

Amsonia tharpii

Family:	Apocynaceae
Common Name:	Tharp's blue-star
Author:	Woods.
Growth Habit:	Subshrub, Forb/herb
CPC Number:	125

Distribution
Protection
Conservation
References

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Photographer: Kathy Rice

Amsonia tharpii is Not Sponsored

Primary custodian for this plant in the CPC National Collection of Endangered Plants is:

Desert Botanical Garden

Kathleen C. Rice contributed to this Plant Profile.

Amsonia tharpii

Plants are herbaceous perennials from a long woody taproot. They become dormant, dying back to the ground during November and emerging from dormancy during March. Leaves are sessile, linear-lanceolate with rounded tips, about 3 cm long and whorled on stems. Flowers are white, clustered at ends of stems, and are followed by two-lobed follicles. As follicles mature, they open completely, becoming flat and papery, dispersing all of the seeds inside except perhaps one remaining at the base of the follicle tube. Seeds are corky and cylindrical, about 1 cm long, and are irregularly truncated at the ends.

Distribution & Occurrence

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State Range

New Mexico
Texas

Habitat

Found in the limestone and gypsum hills of the Chihuahuan desert scrub communities at elevations of 900 to 1,150 meters (3,100 to 3,500 feet). (New Mexico Rare Plant Technical Council 1999)

Distribution

Two very disjunct locations exist within U.S. boundaries--in Pecos County, Texas, and Eddy County, New Mexico. Both are relatively close to the Pecos River, and it could be imagined that this river was the means of seed distribution over such a long distance (USFWS 1990). This species is probably a relictual one, perpetuating itself long after the climate has become increasingly dry and hot.

Number Left

Three populations of this species are known from New Mexico, and possibly one in Texas. Two of the populations in New Mexico are relatively large (over one thousand individuals each), while the third contains fewer than 100 individuals. (New Mexico Rare Plant Technical Council 1999)

Protection

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Global Rank:	G1	4/15/2003	Guide to Global Ranks
Federal Status:	SC	1/19/1996	Guide to Federal Status
Recovery Plan:	No

State/Area Protection

State/Area	Rank	Status	Date
New Mexico			8/29/2002
Texas	S1		4/26/1991

Conservation, Ecology & Research

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Ecological Relationships

Plants contain a milky sap that makes them unpalatable to cattle. (USFWS 1990)

Threats

The area surrounding the canyon where A. tharpii grows in New Mexico appears to have been overgrazed for some time (New Mexico Conservancy 1989). Many trenches, some as deep as five feet and two to three feet wide, have been eroded into the southwest side of the canyon. Grazing has been discontinued for the last several years, and the canopy cover of grasses and forbs has regenerated; however, the presence of dense stands of Prosopis glandulosa saplings and cholla in the canyon bottom are reminders of past overgrazing. Because Amsonia tharpii is found on steep, relatively inaccessible areas along the sides of the canyon, grazing and trampling do not appear to be direct imminent threats. However, plants are subject to extirpation resulting from environmental changes brought about by overgrazing, such as severe erosion resulting in loss of habitat, and change in species composition, resulting in increased competition with non-native species.

The Texas population is situated on an entirely different soil substrate and topography. Plants are found only on one side of a paved road on a flat, open area that has been exclosed to keep out cattle (USFWS 1990). As plants are in the Apocynaceae family and have milky sap, they are unpalatable to cattle, but are still vulnerable to trampling and soil compaction. Plants are also found growing along the highway easement, a narrow strip that is regularly mowed.

Current Research Summary

None known.

Current Management Summary

Management is different for the two sites, but the ultimate result may be the same. At the Bureau of Land Management, New Mexico managed site near Carlsbad, plants are merely checked every year. This may or may not be beneficial, as the soil at that site is extremely friable, almost powdery and fluffy and may becoming more erosive with each subsequent visit (New Mexico Conservancy 1989).
At the Texas site, plants are rarely checked, but they are fenced off from a large empty, rocky pasture. There appears to be a larger number of small-sized plants at this site than at the Carlsbad site.

Research Management Needs

Investigation into reproductive biology is needed, and molecular work to determine diversity within the New Mexico population. Size- and age-class data on these plants is needed, from germination to reproductive maturity, as the size of plants in the wild is primarily resource-dependent.

Ex Situ Needs

Desert Botanical Garden has 600 seeds from the Texas population, and 959 seeds from the New Mexico population. Thirty-three plants grown from seed obtained in Texas have been maintained in pots beneath 30% shade for approximately 10 years. During this time, only seven seeds were produced in cultivation through hand-pollination efforts. Flowering is in April, but not always reliable on a yearly basis, even under controlled conditions in cultivation. Plans for A. tharpii include continuation of seed collection when conditions permit, and further attempts to produce seeds in cultivation.

References

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Books (Single Authors)

Correll, D.S.; Johnston, M.C. 1970. Manual of the vascular plants of Texas. Renner: Texas Research Foundation. 1881p.

Kartesz, J.T. 1993. Species distribution data for vascular plants of 70 geographical areas, from unpublished data files at the North Carolina Botanical Garden.

Kartesz, J.T. 1996. Species distribution data at state and province level for vascular plant taxa of the United States, Canada, and Greenland (accepted records), from unpublished data files at the North Carolina Botanical Garden.

Sivinski, R.; Lightfoot, K. 1994. Inventory of the rare and endangered plants of New Mexico. Santa Fe, NM: New Mexico Forestry and Resources Conservation Division, New Mexico Energy, Minerals and Natural Resources Dept. 46p.

Books (Sections)

Kartesz, J.T. 1999. A synonymized checklist of the vascular flora of the U.S., Canada, and Greenland. In: Kartesz, J.T.; Meacham, C.A., editors. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden. Chapel Hill, NC.

Conference Proceedings

Poole, J.; Janssen, G.K. Managing and Monitoring Rare and Endangered Plants on Highway Rights-of-way in Texas. Gen. Tech. Rep. RM-GTR-283. Proceedings of the Southwestern Rare and Endangered Plant Conference; September 11-14; Flagstaff, AZ. In: Maschinski, J.; Hammond, H.D.; Holter, L., editors. 1996. USDA and US Forest Service. p 8-12.

Sivinski, R.; Knight, P. Narrow Endemism in the New Mexico Flora. Gen. Tech. Rep. RM-GTR-283. Proceedings of the Southwestern Rare and Endangered Plant Conference; September 11-14; Flagstaff, AZ. In: Maschinski, J.; Hammond, H.D.; Holter, L., editors. 1996. USDA and US Forest Service. p 286-296.

Electronic Sources

(1999). New Mexico Rare Plants Information. New Mexico Rare Plant Technical Council: Albuquerque, NM. Version 15. http://nmrareplants.unm.edu/nmrptc/rarelist.htm. Accessed: 2002.

(2000). Center for Plant Conservation's National Living Collection--Profiles. Desert Botanical Garden. http://www.dbg.org/Collections/cpc.html. Accessed: 2002.

Reports

1989. Biological Inventory: Pecos river Canyons Complex Area of Critical Environmental Concern. Prepared for the BLM's FY Challenge Cost-share program by the New Mexico Conservancy.

Rowell, C.M., Jr. 1983. Status report on Amsonia tharpii. Albuquerque, New Mexico: U.S. Fish & Wildlife Service.

Rowell, C.M., Jr. 1983. Status Report on Amsonia tharpii. U.S. Fish & Wildlife Service. p.10.

USFWS. 1990. Status summary for six threatened species. Alburquerque, New Mexico: U.S. Fish and Wildlife Service. p.11.

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This profile was updated on 3/4/2010