Andrena angustitarsata

Justification:
The Narrow-legged Miner Bee (Andrena angustitarsata) is a solitary bee species that occurs in the western United States and extreme southern Canada. Using all verified records of the species, the extent of occurrence is 2,419,178 km2. This species has been described as extremely common in the west, and has been frequently observed in human altered landscapes such as urban gardens, roadsides, and powerline corridors. The species also occurs in grasslands, shrublands, forests, and agricultural areas. The Narrow-legged Miner Bee is able to forage from a wide variety of plant families, but exhibits a strong dietary preference for plants from the families Apiaceae and Rosaceae. Across the range of the species, impacts from climate change, pesticide exposure, increased wildfire severity, and urbanization have been observed. These threats may be acting on the species at local levels. However, because the species is widespread, occurs in many different ecosystems, and has been reported as extremely common, it is unlikely that it is threatened with extinction at this time. As such it is assessed as Least Concern for now.

The Narrow-legged Miner Bee has been described as a dietary specialist in some geographically restricted context, primarily using pollen from the family Apiaceae (Wray and Elle 2016). In a study that examined the dietary breadth of this species along a floral resource gradient, the species was found to alter its diet depending on floral abundance, although a strong preference for pollen from the plant family Apiaceae remained, as well as the addition of the plant family Rosaceae (Kelly and Elle 2021). Both of these studies confirmed dietary breadth through examining pollen scopal loads. Other descriptions of this species refer to it as a generalist, based on visitation of a wide variety of plant families (LaBerge 1989). The species has been shown to exhibit high floral constancy within the genus Lomatium (Apiaceae) (Cane, Weber, and Love 2020), and thus, regardless of its dietary breadth, it likely contributes to significant pollination for this genus in certain settings. This species has been detected in urban environments around Vancouver, British Columbia, including backyards, gardens, parks, powerline corridors and road edges (Tommasi et al. 2004). It is also reported as common in California urban gardens (Frankie et al. 2009). The species has also been recorded in grasslands, shrubland, evergreen forests, and agricultural areas. 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 January through August, with most records from March through June (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Specific threats to this species have not been identified. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena angustitarsata 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 exhibits a strong dietary preference, which may be 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, United States Fish and Wildlife, 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.