Andrena apacheorum

Justification:
Andrena apacheorum is a pollen specialist bee that occurs mostly in the Four Corners region of the US, with some records from adjacent states as well. The extent of occurrence (EOO) for this species is 1,246,303 km2. There are limited recent observations of this species, although this may be an effect of limited search effort where the species occurs. Within the range of the species, climate change impacts, increased urbanization and agricultural development have been observed, so it is possible that localized threats are acting on this species. More information is needed to assess the population trend and range extent for this species. However, because the species is widespread and occurs in different ecoregions, it is unlikely that it is threatened with extinction at this time. Therefore, it is assessed as Least Concern.

There is little information about the habitat and ecology of Andrena apacheorum. The species has been described as a pollen specialist, and visits plants from the family Asteraceae, notably Cirsium, Ericameria, Erigeron, Senecio, and Solidago, but has also been associated with plants from the families Geraniaceae, Lamiaceae, and Phrymaceae. This species likely nests underground like all other Andrena (Danforth et al. 2019), but nests for 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). Adults have been observed from May through October, although the majority of records are from July and August (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019). Habitat:

Since 2000, the Southwest United States 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). A recent study has shown reduced diversity and abundance of native bees under drought conditions (Hung et al. 2021). Two states within the range of this bee are expected to have their human populations increase significantly in the next twenty years (32% increase in Colorado, and 35% in Utah; Weldon Cooper Center for Public Service, University of Virginia 2022). Housing development needed to meet these increases will undoubtedly threaten habitats used by this species. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena apacheorum 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 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).

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, and National Park 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 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?)