Andrena chylismiae

Justification:
Andrena chylismiae is a solitary bee that occurs in the Great Basin region of the United States, from southeast Oregon south to eastern California, east across Nevada to Wyoming. Using all available observations, the extent of occurrence (EOO) is 268,955 km2, and the area of occurrence (AOO) is 44 km2. Although there were over 250 observations of this species used in the revision, fewer than 20 were available as digitized specimen records. Thus the EOO and the AOO are likely underestimated. Additionally, this species has not been observed since 1997. It is unclear the extent to which this species still occurs in its historic range. This species is a dietary specialist, using pollen from the plant genus Camissonia for pollen. It occurs in shrubland, which within its range, sees high grazing pressure, contributing to habitat degradation. In addition to overgrazing, climate change and exposure to pesticides has been observed within the range of this species. These threats may be acting on the species at local levels. RANK SENTENCE

Food habits comment: Andrena chylismiae is a dietary specialist that collects pollen from the plant genus Camissonia (Onagraceae) for its offspring (LaBerge and Thorp 2005). Habitat comment: This species has been recorded in shrubland. Reproduction comment: This species likely nests underground like all other Andrena (Danforth et al. 2019), but nests from this species have not been described. Nest cells from other members of this genus are located at the ends of the lateral burrows, which are typically lined with a waxy Dufour’s gland secretion (Cane 1981) that serves to both isolate the provision from pathogens in the surrounding soil and to regulate water uptake from the soil atmosphere (Cane and Love 2021). Females provision each cell with a ball of pollen moistened with nectar on which they lay a single egg (Michener 2007). Phenology comment: Records of this species come from May and June (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Threat comments: Specific threats to this species have not been identified. This species may be impacted by severe drought. Since 2000, the Southwest U.S. has seen the worst drought in 1200 years (Williams, Cook, and Smerdon 2022). Drought can reduce the abundance of flowering plants on a landscape scale, and also reduce pollen and nectar quality (Wilson Rankin, Barney, and Lozano 2020). Drought conditions have been shown to reduce the diversity and abundance of native bees (Minckley, Roulston, and Williams 2013; Hung et al. 2021). This species may also be impacted by grazing practices on public lands. The center of this species range is Nevada, most of which is owned and managed by the Bureau of Land Management (BLM), and is actively grazed. Certain grazing practices may impact the stability of this species.Two documented localities for this species come from BLM grazing allotments that are failing to meet the agency's own land health standards, with their failure attributed to grazing. Three other localities of the species occur on grazing allotments that fail the land health standard for various other reasons (BLM 2022). Habitat degradation, caused by livestock overgrazing, exotic species invasion, or fire regime change, may limit the availability of host plants and nest site locations for this species. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena chylismiae is a ground nesting species, and nests may be harmed by certain agricultural practices such as tilling, which can kill bees nesting close to the surface (Williams et al. 2010). This species is a dietary specialist, which has been linked to higher risk of extinction due to reduced host plant availability, especially under climate change scenarios (Roberts et al. 2011) and reduced effective population sizes (Packer et al. 2005). Additionally, Andrena have been reported to have low reproductive output because of the short adult life span, and a low rate of brood cell provisioning (reviewed in Danforth et al. 2019). Other threats to bees generally include habitat loss or modification, climate change, pesticide use, exposure to pathogens from managed bee species, and competition with honey bees (Brown and Paxton 2009; Potts et al. 2010; Wojcik et al. 2018; Grab et al. 2019; Raven and Wagner 2021).

Conservation needs No known conservation actions are in place for this species. Protected/Managed area comment: Observations of this species are known from Bureau of Land Management (BLM), National Forest Service, and Department of Defense land, but this does not confer any specific protections to the species. Management comment: Specific conservation needs for this species have not been identified. Due to the importance of supporting wild bee populations for pollination services, general conservation practices are recommended including, restoring, creating, and preserving natural high-quality habitats to include suitable forage and nesting sites; limiting pesticide use on or near suitable habitat, particularly during the adult bee’s flight period; promoting farming and urban practices that increase pollinator-friendly plants in margin space; minimizing exposure of wild bees to diseases transferred from managed bees; and lastly, avoiding honey bee introduction to high-quality native bee habitat.

Research need comment: More information is needed about the population status, population trend, existing threats, range limits, habitat, and ecology of this species. Surveys targeting this species are needed throughout its range to determine its persistence throughout its historic range.

(a. any taxonomic concerns about the validity of the species? b. any taxonomic revisions underway that would require a species reassessment.