Andrena amphibola

Justification:
The Ambiguous Miner is a solitary bee species that occurs in the western United States and Canada, in forests, shrublands, and agricultural, suburban, and urban areas. The species is a dietary generalist, and has been observed foraging from a wide variety of plant families. Using all records of the species, the extent of occurrence is 3,275,974 km2. There are limited records since 2014, but these records come from wide ranging localities across the extent of occurrence. Across the range of the species, threats from climate change, altered fire regime and increased fire severity, and exposure to pesticides has been observed. These factors may be acting on the species at local levels. Because the species is widespread and occurs in many different habitats, it is unlikely that it is threatened with extinction at this time. As such, it is assessed as least concern for now.

Andrena amphibola is a dietary generalist solitary bee that has been recorded foraging from a wide array of plant families. It has also been detected in small numbers foraging from the genus Toxicoscordion (Melanthiaceae), the pollen and nectar of which is considered toxic to many bee species due to the presence of some neurotoxic alkaloids (Cane 2018). This suggests that Andrena amphibola may have evolved some tolerance to these chemicals, although it does not specialize within the plant genus. The species occurs in evergreen forests of western Mountain ranges, shrublands of the Great Basin, and agricultural, urban and suburban areas throughout its range. 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 June and July (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 amphibola 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. Observations of this species are known from Bureau of Land Management (BLM), U.S 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.