Andrena primulifrons

Justification:
Andrena primulifrons is a solitary bee that occurs in the southwestern United States and Northern Mexico. It is a dietary specialist, visiting plants chiefly from the genus Physaria (Brassicaceae) for pollen. Using all known records of the species, the extent of occurrence is 1,217,899 km2. There have been limited recent records of this species. Records from the last decade come from just one locality near Laredo, TX. Although records from the last two decades include more localities across several states, the persistence of this species throughout its historic range is not well understood. Lack of recent records may be an effect of limited sampling effort for bees within the range of this species. The narrow dietary breadth of this species, coupled with drought and climate change, and impacts from urbanization may present some threats to this species. More information is needed to assess the population trend, impacts of threats, and to determine the persistence of this species throughout its historic range. Because the species is widespread, and can apparently be locally abundant, it is assessed as Least Concern for now.

Andrena primulifrons is a dietary specialist solitary bee that visits plants from the family Brassicaceae, mostly within the genus Physaria, for pollen. The species can be found in desert shrublands and grasslands, (Kazenel 2022), as well as croplands 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 to May, with most records from March and April (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019). Parasitism by Stylops pascarellai has been reported in this species (Zabinski 2023).

Since 2000, the Southwest U.S. has seen the worst drought in 1200 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). Because Andrena primulifrons has a short adult life stage, emerges in spring, and appears to be a narrow pollen specialist, of the plant Physaria which blooms in response to winter rain, it may be at further risk from winter droughts within its range. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena primulifrons 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 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), US Forest Service, US Fish and Wildlife land, US 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 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.

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.