Andrena biscutellata

Justification:
Andrena biscutellata is a solitary bee species that occurs in the central United States, from eastern New Mexico and Colorado east across Texas, Oklahoma, and Kansas. Using all observations, the extent of occurrence is 548,277 km2. There are limited observations of this species overall, and few since 2014. The species is presumed to be uncommon, but limited records overall may be due to limited search effort for bees generally where the species occurs. Andrena biscutellata is a narrow dietary specialist, collecting pollen from the plant tribe Heliantheae (Asteraceae). It occurs in shrubland, grasslands, and agricultural areas. Across the range of the species, impacts from climate change, habitat loss and degradation, 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 occurs in several habitat types, it is unlikely that it is threatened with extinction at this time. As such, it is assessed as Least Concern.

Andrena biscutellata has been described as a narrow dietary specialist, visiting plants from the tribe Heliantheae (Asteraceae) for pollen (Larkin, Neff, and Simpson 2008). The species has been recorded from shrubland, grassland, 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 April through October, with most records from June (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 biscutellata 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. There are no known records of this species from federally protected lands. 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.