Lepidium papilliferum

Lepidium papilliferum is an annual or biennial taprooted herb that is endemic to southwestern Idaho in the western United States. It is restricted to unique small-scale openings within sagebrush-steppe habitats. While there are over 100 sites known, it has declined over the last 100 years due land conversion and habitat degradation. Rangewide, this species is threatened by on-going habitat loss and degradation due to the invasion of non-native species and the increased frequency and severity of wildfires, but also grazing livestock and development. Plants are directly impacted by competition with invasive plants, trampling by livestock, and seed predation by ants. The seedbank is important for persistence of the species, thus factors that impact reproductive success, including low pollinator numbers, fragmented habitat limited genetic transfer, and unfavorable climate conditions are important considerations for its management.

Lepidium papilliferum occurs in the western United States where it occurs in southwestern Idaho in Great Basin sagebrush steppe habitats on the Snake River Plain and Foothills geographic areas and a disjunct population on the Jarbidge geographic area, approximately 40 miles south (USFWS 2007, 2021). It is documented in multiple counties: Ada, Canyon, Gem, Elmore, Payette, and Owyhee counties.

The greatest threats to this species are the invasion of annual grasses, like Cheatgrass (Bromus tectorum), and the subsequent increase in fire frequency and intensity (USFWS 2007, 2021). Invasive annual grasses not only contribute to the decline of habitat quality but also displace native species including Lepidium papilliferum (USFWS 2021). Fuel breaks may lower the threat of fire but their creation contributes to the loss of habitat and potentially disturbance favoring invasive species. Climate change is believed to have played a role in increasing fire frequency and the spread of invasive species but may impact the species reproductive success through unfavorable climate conditions into the future (USFWS 2021). Development is a threat in Foothills and Snake River Plain geographic areas, where at least 20 occurrences on private land are directly threatened by habitat conversion (USFWS 2021). Livestock trampling directly impacts plants and the slickspot habitat and is largely a threat to occurrences on Federal and State owned lands (USFWS 2021, Meyer et al. 2006). When the habitat is wet, concentrations of livestock in the slickspots, can damage the soil structure and disrupt or destroy the seedbank (USFWS 2021). Seed predation by native ants, specifically the Owyhee Harvester Ant (Pogonomyrmex salinus), can impede the replenishment of the seedbank, potentially causing the extirpation of small sites (USFWS 2021). Many of these threats also contribute to the increased fragmentation of habitat and simultaneously creating barriers, reducing genetic exchange between populations (USFWS 2021). Preserving ample native flowering vegetation and appropriate distances between sites in important to support pollination, the primary mechanism for genetic exchange (USFWS 2021).