Andrena atypica

Justification:
Andrena atypica is a dietary generalist solitary bee species that occurs in California, United States, and Baja California Norte. Using all records of the species, the extent of occurrence is 176,067 km2. This species has not been observed since 2011, despite there 15 times as much search effort within its EOO as was needed to detect it historically. However, search effort has not been evenly distributed across its range, and there are limited Andrena records from the flight periods of this species in the center of its range. There may be additional data for this species in unidentified museum material, or undigitized records, contributing to uncertainty of its status. The species occurs in an endangered shrub ecosystem that is threatened by habitat loss and modification, as well as in forests, agricultural areas, and urban areas. Across the range of the species, impacts from drought, altered fire regime, habitat loss and modification, and exposure to pesticides has been observed, and may be acting on the species at local levels. More information is needed to determine a population trend, understand the life history of the species, and understand the degree to which these threats are acting on the species. As such it is assessed as Data Deficient for now..

Andrena atypica is a dietary generalist solitary bee that appears to have some preference for plants from the following genera: Cryptantha (Boraginaceae), Salix (Salicaceae), Rhus (Anacardiaceae), as well as Rhamnus and Ceanothus (Rhamnaceae) (LaBerge and Ribble 1972). The species has also been observed foraging at Quercus dumosa, a vulnerable California oak species (Buchmann, Adams, and Howell, A, Weiss, M 2010). It has been recorded in shrublands, evergreen forest, and agricultural 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 February through July, with most records from April (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Specific threats to this species have not been studied. However, climate change and drought, urbanization, and altered fire regime impact the quality of the habitat where this species occurs. Since 2000, the Southwest U.S. has seen the worst drought in 1,200 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 occurs in California coastal sage scrub habitat, one of California's most threatened vegetation types, which is globally imperiled (NatureServe 2024). This habitat is highly threatened by modification, fragmentation, and loss due to urban and suburban growth. Nearly half of California’s residents live in the coastal California counties where this habitat occurs, which is less than 10% of the state’s land area (Riordan and Rundel 2013). Less than 20% of this habitat remains (Davis, Stine, and Stoms 1994), and the existing fragments are considered some of most valuable real estate in California. This contributes to considerable development pressure on remaining fragments, and their high real estate value makes their conservation costly. Coastal sage scrub has also been modified significantly in the past 100 years due to exotic annual grass invasion, which has been facilitated by increased wildfire frequency (Minnich and Dezzani 1998; Talluto and Suding 2008). These factors also contribute to a feedback where increased grass cover increases fire frequency, leading to grassland conversion. This habitat conversion may limit the availability of host plants used by Andrena atypica and alter other abiotic factors important for this species. Additionally, this species may be impacted by agricultural intensification, including high exposure to pesticides where it occurs in California’s Central Valley. The species has been recorded in at least one study of pollinators found in almond orchards in central California (Klein et al. 2012). The Central Valley of California is one of the most intensively farmed regions in the U.S.(Katibah 1984). An estimated 71% of the Central California Valley ecoregion is devoted to agriculture (Soulard and Wilson 2015). This species may be impacted by high exposure to pesticides where it occurs in the Central Valley. This region has some of the nation’s highest pesticide inputs, which can be detected in non-target plant species, sometimes in insect-lethal concentrations, across all land use types (Halsch et al. 2020). Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena atypica 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). 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), United States Forest Service, United States Fish and Wildlife, and National Park 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.