Deseret Milk-vetch

Astragalus desereticus

Description

The Deseret milk-vetch is a perennial, herbaceous, almost stemless flowering plant. It grows 2-6 in (4-15 cm) tall, and arises from a caudex (a short, persistent stem growing just under the soil surface). The leaves are 2-4 in (4-11 cm) long and are pinnately compound (being composed of 11-17 leaflets arranged along a common petiole, giving an overall feather-like appearance). Each leaflet is elliptic to ovate in shape, and has a dense, silvery-gray pubescence of short hairs on both sides. The flowers are 0.7-0.9 in (1.8-2.2 cm) long, white in color with a purple tip on the keel, and borne as an inflorescence of five to 10 flowers. The ripe seedpods are 0.4-0.8 in (1-2 cm) long, densely covered with lustrous hairs, and contain 14-16 seeds.

The flowers of the Deseret milk-vetch are probably pollinated by native bumblebees (Bombus spp.). Many species of Astragalus are poisonous to grazing mammals, due to the presence of selenium-containing compounds, toxic alkaloids, or nitrotoxins. The Deseret milk-vetch, however, appears to not be toxic to cattle, and is therefore vulnerable to overgrazing.

Habitat

The Deseret milk-vetch occurs on steep south-and west-facing slopes. It grows in soil characterized by coarse, crudely bedded conglomerate. Its plant community is dominated by pinon pine (Pinus edulis ) and Utah juniper (Juniperus osteosperma ).

Distribution

The Deseret milk-vetch is a locally evolved (or endemic) species whose only known population grows on a sandstone outcrop above the town of Birdseye, Utah County, Utah.

Threats

The original collection sites of the Deseret milk-vetch no longer exist. The only known population consists of 5,000-10,000 individuals growing in an area of less than 300 acres (120 hectares), extending about 1.6 mi (2.6 km) by 0.3 mi (0.5 km). The critical habitat of the Deseret milk-vetch is owned by the State of Utah and three private land owners. The rare plant is threatened by grazing and trampling by livestock, destruction of its habitat by residential development and road widening, and catastrophic events such as wildfire, which could decimate its small population.

Conservation and Recovery

Although it is threatened, The Deseret milk-vetch is not protected. Landowners of the critical habitat have been contacted and informed of the presence of this rare plant and of the need to conserve its habitat, but they have not committed to do so. Conservation of the Deseret milk-vetch requires that its critical habitat be acquired, or conservation easements negotiated, so that its critical habitat can be set aside as an ecological reserve and protected from development and grazing.

Contact

U.S. Fish and Wildlife Service, Utah Ecological
Services Field Office
Lincoln Plaza Suite 404, 145 East 1300
South Salt Lake City, Utah 84115
Telephone: (801) 524-5001

Reference

U.S. Fish and Wildlife Service. 1999. "Endangered and Threatened Wildlife and Plants; Final Rule to List Astragalus desereticus (Deseret milk-vetch) as Threatened." http://endangered.fws.gov/r/fr99668.html