Andrena bocensis

Justification:
Andrena bocensis is a solitary bee known from approximately 80 observations that occurs in northern California and southern Oregon, United States. Using all observations, the extent of occurrence is 13,052 km2. The species has not been observed anywhere in its range since 1965, and it is unclear if the species is extant. Andrena bocensis is a dietary specialist, foraging from the plant genus Chrysothamnus to provision nest cells. It has been recorded in forest edges and shrublands. Within the EOO of this species, the Bureau of Land Management has reported approximately 900 km2 of grazing allotment land has failed to meet the agency’s own standard for land health, the majority of failures having been attributed to grazing practices. Although the host plants of this species may not be impacted by overgrazing, there are likely other impacts of overgrazing, including degradation of nesting sites, that are acting on the species. Andrena bocensis is known from just nine localities, contributing to a maximum of nine locations if threats from habitat degradation act independently on each locality. Because the species is known from a small EOO, with limited locations, and documented decline in quality of habitat across its range due to livestock overgrazing and other causes, this species is ranked as Vulnerable B1abiii. More information is needed to determine if this species is still extant in its range, and if so, to describe and mitigate its threats.

Andrena bocensis is a dietary specialist, collecting pollen from the plant genus Chrysothamnus to feed its larvae (Donovan 1977). 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 July through September (Chesshire et al. 2023; Donovan 1977). Adults are assumed to emerge annually (Danforth et al. 2019).

Specific threats to this species have not been identified. Some records of this species come from areas adjacent to crop land, where they may be exposed to pesticides. Within the EOO of the species, over 900 km2 of grazing land managed by the Bureau of Land Management has failed to meet the agency’s standard for land health, and in many cases that failure has been attributed to grazing practices (BLM 2022). Although the host plants of the species may not be impacted by overgrazing or other disturbance (McArthur and Taylor 2004), habitat degraded by overgrazing may present other threats to the bee, such as streambank trampling and soil compaction, which increases soil erosion, streambank incision, and lowers the water holding capacity of soils (Dwire et al. 1999; Kauffman and Pyke 2001). Compaction of the soils from cattle can also limit the abundance of suitable bee nesting sites (Kimoto et al. 2012; Thapa-Magar, Davis, and Fernández-Giménez 2022). Additionally, grazing contributes to exotic species invasion by dispersing plant propagules or creating favorable conditions for invasion ((Reisner et al. 2013; Olff and Ritchie 1998; Chambers et al. 2014). Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena bocensis 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. Observations of this species are known from United States Fish and Wildlife and National 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.