Andrena frigida

Justification:
The frigid mining bee (Andrena frigida) is an early spring-emergent, pollen specialist solitary bee species that occurs across much of Canada and the United States. The extent of occurrence using all known occurrences of this species is 15,086,001 km2. Since 2000, there have been only 12 observations of this species west of the Rocky Mountains. There are 675 historic observations from this same region, from every decade since 1890. The lack of recent records may be a result of limited sampling effort, especially during the flight period of this species, which is earlier than most other bees. However, the persistence of this species throughout its entire range is uncertain. The frigid mining bee is a pollen specialist bee within the riparian associate genus Salix, and as such may be impacted by riparian habitat loss in the west. Within the range of the species, climate change impacts, increased urbanization and agricultural development have also been observed, so it is possible that localized threats are acting on this species. More research is needed to determine population trends and threats to this species. 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.

The frigid mining bee is an early spring active dietary specialist that visits willows (Salix spp., Salicaceae) for pollen. This species has the ability to fly with unusually low thoracic temperatures, likely an adaptation to early spring emergence in cool climates (Bishop and Armbruster 1999). This species occurs in taiga, forests, grasslands, mountains, foothills, shrublands and coastal areas. Although there are historic observations from the southwest United States, these records come from higher elevation forests and shrublands, not valley deserts. 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 (J. H. Cane 1981) that serves to both isolate the provision from pathogens in the surrounding soil and to regulate water uptake from the soil atmosphere (James H. 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 February through July, but mostly from March to early June (LaBerge 1980; Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019). Habitat:

Threats to this species have not been well defined. It is possible that this species is not as common as it once was in the western and southern part of its range, an area that has been impacted by major drought in the last 20 years. Since 2000, the Southwest US 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). Drought conditions have been shown to reduce the diversity and abundance of native bees (Hung et al. 2021). Drought and climate change may be particularly impactful for this species, as it depends on riparian associated Salix species as its host plant. Due to dams and river diversions, drought, and groundwater pumping, the vegetation in these riparian areas has changed dramatically in the last century (Ohmart 1994; Krueper 1993). Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena frigida 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 oligolectic, 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). This species has had its conservation status evaluated using NatureServe criteria at the U.S. state and Canadian province level in some areas where it occurs. It has been evaluated as Vulnerable in Ontario, Canada, and in New York and Connecticut, U.S.

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, United States Fish and Wildlife 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 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.

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