Andrena aurihirta

Justification:
Andrena aurihirta is a solitary bee species that occurs in the southern half of California, United States. It has been recorded foraging from plants in the family Asteraceae, but the dietary breadth of this species is not well understood. Using all observations of the species, the extent of occurrence is 38,721 km2. The species has not been recorded anywhere in its range since 1993, there have been no Andrena records from any species from the EOO in the appropriate flight period, suggesting that the absence of recent records may be due to insufficient recent search effort. Across the range of the species, impacts from habitat loss and degradation, climate change, and exposure to pesticides has been observed. These threats may be acting on the species at local levels. More information is needed to determine the persistence of this species through its range, its population trend, and to better understand its life history. As such, it is assessed as Data Deficient.

All associated floral records for this species come from the plant family Asteraceae, including the genera Chrysothamnus, Ericameria, Gutierrezia, Isocoma, and Solidago, but the dietary breadth of this species has not been confirmed to be restricted within this family. This species has been described as restricted to the high mountain areas of southern California (Donovan 1977), although some observations come from low elevation localities and valleys. It has been recorded from evergreen forests, shrublands, grasslands, and urban areas. 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). Records of this species come from September and October (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019). Several types of parasitism have been observed in this species, including an observation of a stylops, and several observations of triungulins (Donovan 1977).

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). Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena aurihirta 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 may be 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. Observations of this species are known from Bureau of Land Management (BLM) and United States Forest Service land, but this does not confer any specific protections to the species. Further research is needed to determine the overall size of the population and to identify trends and existing threats. 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.

Surveys targeting this species are needed throughout its range to determine its persistence throughout its historic range. More information is needed about the population status, range limits, habitat, and ecology of this species.

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