Andrena anograe

Justification:
Andrena anograe is a dietary specialist solitary bee that occurs in the Mountain West of the United States. Using all verified records of the species, the extent of occurrence is 298,236 km2. This species has not been observed since 2012, with limited records of the species from the last 20 years, although there has apparently been enough search effort to detect the species since it was last observed. The species visits members of the plant genus Oenothera (Onagraceae) for pollen, and occurs in cold deserts and arid shrublands. Across the range of the species, impacts from climate change, urbanization, and pesticide exposure. These factors may be acting on the species at local levels. Although the species is relatively widespread, and occurs in several different habitat types, it has not been observed recently. As such it is assessed as Data Deficient for now.

Andrena anograe is a dietary specialist species that visits members of the plant genus Oenothera for pollen, chiefly Oenothera caespitosa, O. albicaulis, and O. scapoidea (LaBerge and Thorp 2005). This genus of plants is adapted for pollination by hawkmoths, and as such, species of this genus have large grained pollen that is connected with cobweb like threads. This type of pollen is difficult to handle for most generalist bee species. Andrena anograe, and other bees that specialize within this genus, have adapted to this issue by having sparse scopal hairs that make pollen packing easier (LaBerge and Thorp 2005). In a study on the reproductive ecology of Oenothera caespitosa, Andrena anograe is described as primarily a pollen thief of the plant, not largely contributing to seedset, although the bee may serve as a conditional pollinator when they are abundant or when certain floral morphology is present (Artz, Villagra, and Raguso 2010). Andrena anograe has been recorded in the arid shrublands and cold deserts of the Colorado plateau, southern Rocky Mountains, and northwestern Great Plains. 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 September, with most records from May (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 anograe 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), United States Forest Service, and 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 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.