Andrena colletina

Justification:
Andrena colletina is a pollen specialist bee species that occurs in the western United States and southwestern Canada. The species has been recorded from shrublands and open forests, and uses pollen from the plant family Asteraceae. Using all known records for the species, the extent of occurrence is 2,700,394 km2. However, the species has not been recorded since 2012, despite over eight times as much search effort within its range as was required to detect it prior to 2013. Climate change, increased urban development, and habitat loss may present threats to this species on a local level. However, because A. colletina is widespread, occurs in many different ecoregions, it is unlikely that it is threatened with extinction at this time. Although dietary specialization may contribute some risk with regard to extinction risk, the host plants of A. colletina are widespread, abundant, and have long bloom periods. As such, it is assessed as Least Concern for now.

Andrena colletina is a pollen specialist bee, using pollen from the plant family Asteraceae, with observations from the genera Solidago, Chrysothamnus, and Ericameria. 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 as early as May to as late as October, but most records are from August and September (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019). Habitat:

There are no specific threats described for this species. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena colletina 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 pollen 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 and 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).

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, Fish and Wildlife 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 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.