Report on the conservation status of Lepidium davisii

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Abstract:

Lepidium davisii (Davis' peppergrass) is a regional endemic, known to be extant at 293 sites and extirpated from at least two others. The populations are scattered throughout an area of southwestern and south-central Idaho, north-central Nevada, and southeastern Oregon that is approximately 180 miles long by 90 miles wide. Within this area, populations occur in six disjunct clusters or distribution centers: Mountain Home Desert (Idaho), Bruneau Desert (Idaho), Salmon Falls Creek (Idaho), South Fork Owyhee River (Idaho, Nevada, Oregon), Alvord Desert (Oregon), and Barren Valley (Oregon). Its habitat is a unique wetland community: a vernal lake or playa, which can be filled with water in the spring and dry and hard as concrete in the summer. Lepidium davisii populations in the Mountain Home Desert distribution center show a decline and are the most vulnerable to extirpation. The overall cause of the decline is the poor ecological condition of the sagebrush-steppe ecosystem on the western Snake River Plain. There is no reversal in this trend in the foreseeable near future. Populations in the other five distributions centers appear stable. Due to the documented extirpation and declines in populations and habitat on the Mountain Home Desert, it is recommended that L. davisii be changed from a category 2 candidate to a category 1 candidate. While it is apparently stable and more or less secure in five of the six distribution centers, one entire disjunct segment of its distribution is in jeopardy. Preliminary evidence indicates that there may be genetic differentiation between populations and distribution centers, and the fact that the Mountain Home Desert populations occupy the elevational and aridity extremes for the species as a whole makes these populations an important evolutionary unit whose conservation must be addressed. The Idaho Department of Parks and Recreation should pursue a Conservation Agreement with the Lower Snake River District BLM, Idaho Army National Guard, Idaho Department of Lands, and Mountain Home Air Force Base to maintain viable populations of L. davisii on the Mountain Home Desert. Detailed discussions on the taxonomy, distribution, abundance, habitat requirements, conservation status, and recommendations to federal and state agencies are included in this report.

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PLANT EF: LEPIDIUM DAVISII; ELECTRONIC FILE - Plants (without appendices)

SWAP (2/19/2016) citation:
Moseley RK. 1995. Report on the conservation status of Lepidium davisii. Boise (ID): Idaho Department of Fish and Game, Conservation Data Center. 34 p. Status survey report prepared for Idaho Department of Parks and Recreation.