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Tahoe draba (Draba asterophora var. asterophora) is a small alpine perennial plant in the Brassicaceae (mustard) family. The species has small yellow flowers, and is characterized by a pincushion growth form where all the foliage grows close to the ground in a short mound or mat (Baad 1979). The worldwide distribution of Tahoe draba is limited to high elevation (greater than 8,000 feet) steep, north-facing talus slopes in or near the Lake Tahoe Region (Schlesinger and Holst 2000). Two historical populations were reported south of the Region (Mt. Gibbs in Yosemite and near Sonora Pass), but these have not been relocated since they were recorded in 1916 and 1936 respectively (Engelhardt and Gross 2013). Within the Tahoe Region, the species is found in four main populations located around Mount Rose in the north, and the Freel Peak/Jobs Sister and Monument Peak areas in the south, with approximately 41 subpopulations (McKnight and Rowe 2015). A recent genetic study found that the northern and southern populations of Tahoe draba are genetically distinct: northern populations are polyploid while southern populations are diploid (Putnam 2013). The author of this study recommends treating these populations as separate taxonomic entities, along with Cup Lake draba (Draba asterophora var. macrocarpa) (Putnam 2013). Although there are a few occurrences located adjacent to the Lake Tahoe Region in the Humboldt-Toiyabe National Forest, the largest number of plants occur in the Tahoe Region populations; thus the status of Tahoe populations is critical to the viability of the entire species. Tahoe draba is a threatened species in California (California Department of Fish and Wildlife 2015) and Nevada, and is considered imperilled globally (Nevada Natural Heritage Program 2015b).

Human and Environmental Drivers

Human activities that pose direct threats include recreational activities that might trample or uproot plants (e.g., camping, hiking, equestrian use, trail construction, snowmobiles), and the construction and maintenance of ski resort facilities (California Department of Fish and Wildlife 2015). Trampling of Tahoe draba at Freel Peak, a popular hiking destination, has been observed (Putnam 2013, McKnight and Rowe 2015). Snowmobile traffic may increasingly be cause for concern at the Mount Rose and Freel Peak/Jobs Sister areas due to decreased snowpack (Engelhardt and Gross 2011a). Tahoe draba is found at both Heavenly Ski Resort and Mount Rose Ski Tahoe where construction and maintenance of ski facilities have the potential to directly impact population sites. Results from one study indicate that grading of ski runs is correlated with lower plant densities, smaller plant sizes, and higher annual mortality rates (Engelhardt and Gross 2013, Putnam 2013). Changes in precipitation type, timing, and quantity associated with climate change may have significant impacts on Tahoe draba distribution and abundance (Smith et al. 2008). Decreased snowpack and/or earlier snowmelt have the potential to impact populations by altering plant community composition and species interactions, and decoupling plant flowering periods and insect pollinator visitation.

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