Andrena chalybiodes

Justification:
941,692 km2 Andrena chalybiodes is a solitary bee that occurs in the western United States, from Washington south to southern California, and east to Utah. Using all observations of the species, the extent of occurrence is 941,692 km2. However, it has only been observed once since 1972. It is unclear if it persists throughout its entire known range. The species is a dietary specialist within the plant family Asteraceae, and may have a diet even further restricted within the genus Agoseris. It has been observed in grasslands, shrublands, evergreen forests, and urban areas. Across the range of the species, threats from habitat degradation and loss, climate change, and exposure to pesticides have been observed. These threats may be acting on the species at local levels. More information is needed to understand the life history of this species, and to better understand the degree to which threats are acting on the population. As such, this species is assessed as Data Deficient for now.

Andrena chalybiodes is a dietary specialist that uses pollen from plants in the family Asteraceae, primarily from the genus Agoseris, which contains many species native in the range of the species (Thorp 1969). The bee has also been observed foraging from other ligulate Asteraceae species including the introduced Taraxacum officinale and Hypochaeris radicata (Thorp 1969). The species has been observed in grassland, shrubland, evergreen forest, 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 March through June, with the majority of observations from May (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena chalybiodes 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 National Park Service 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.