Andrena brevicornis

Justification:
Andrena brevicornis is a solitary bee known from approximately 45 observations. It occurs in Texas and Oklahoma, United States, and may also occur in Mexico, although it has not been recorded there. Using all records, the extent of occurrence is 381,057 km2, however, observations since 2014 have only been recorded in Oklahoma. Its population status across its entire known range is not well understood. It has been recorded foraging from a wide range of plants, and occurs in shrublands and agricultural areas. Across the range of this species, impacts from climate change, habitat degradation and loss, and exposure to pesticides have been observed. These threats may be acting on the species at local levels. However, because the species is widespread, and likely occurs in more than 10 locations, it is unlikely that it is threatened with extinction at this time. As such, it is ranked as Least Concern for now.

There is little information about the dietary breadth of the species. It has been recorded foraging from a number of plant genera, including Rhus (Anacardiaceae); Macaraenthera, Bahia, Thelesperma (Asteraceae); Prosopis, Senegalia (Fabaceae); and Phacelia (Boraginaceae) (Bouseman and LaBerge 1978). The species has been observed in shrublands and agricultural 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 and April (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Since 2000, the Southwest U.S. has seen the worst drought in 1200 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). Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena brevicornis 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. There are no records of this species from any federally managed land, but has been recorded from Roman Nose State Park, OK, and Welder Wildlife Refuge, TX. 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.