Andrena evoluta

Justification:
Andrena evoluta is a pollen specialist bee that occurs across much of the Intermountain West of the United States. The extent of occurrence (EOO) based on verified records is 1,041,641 km2, although there is only one observation of this species since 2004. This is likely a result of limited search effort throughout the entirety of the species’ range, rather than a true absence. Although it is a dietary specialist, which can be linked to higher extinction risk, it specializes within the species rich plant family Asteraceae, so host plants are likely abundant, widespread, and bloom throughout the adult flight period of this species. Within the range of the species, impacts from climate change, urbanization, and agricultural development have been observed, so it is possible that localized threats are acting on this species. However, because the species is widespread and occurs in many different ecoregions, it is unlikely that it is threatened with extinction at this time. Therefore, it is assessed as Least Concern.

Andrena evoluta is a pollen specialist bee of plant species in the family Asteraceae. It has been recorded foraging on the genera Arnica and Crepis in Washington state (Wilson et al. 2010), and Taraxacum, Agoseris, and Senecio in Utah (Carril et al. 2018). Observations come from dry highland forests, foothills, shrublands, and grasslands. This species likely nests underground like all other Andrena (Danforth et al. 2019), but nests of 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 April through July, with most observations from June and July (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019). Habitat:

Specific threats to this species are not known, however climate change impacts may be altering the habitat of A. evoluta. Since 2000, the Southwest U.S. has seen the worst drought in 1,200 years (A. P. 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 evoluta 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 (N. M. Williams et al. 2010). This species is oligolectic, 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). This species has had its conservation status evaluated using NatureServe criteria at the Canadian province level in some areas where it occurs. It has been evaluated as Vulnerable in British Columbia, Canada.

No known conservation actions are in place for this species. Observations of this species are known from Bureau of Land Management (BLM), National Park Service (NPS), and United States Forest Service (USFS) 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 better understand 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.

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