Andrena barbilabris

Justification:
Andrena barbilabris is a holarctic bee that occurs across the United States, Canada, and much of Europe. Using all observations of the species, the extent of occurrence is 42,254,248 km2, with observations since 2014 relatively well distributed across the range of the species, including on both continents. The species forages from a wide range of plant families, with plants from the genera Salix and Prunus are among the most common forage. The species nests in large aggregations in sandy soil, where it can face high parasitism pressure. It has been recorded in grasslands, shrublands, forest, agricultural lands, and urban areas. Across the range of the species, impacts from habitat degradation and loss, climate change, and exposure to pesticides have been observed. These threats may be acting on the species at local levels. However, because the species is very widespread, forages from a wide variety of plants, and has been recently observed in many localities, it is unlikely that it is threatened with extinction at this time. As such, it is assessed as Least Concern.

Andrena barbilabris forages from a wide variety of plant species, many of which are trees or shrubs (Boyes, Rowntree, and Coulthard 2024). It has been recorded foraging from the plant families Asteraceae, Boraginaceae, Brassicaceae, Corncaceae, Rosaceae, Ranunculaceae, Rhamnaceae, and Salicaceae, among others. It may show a preference for plants from the genera Salix (Salicaceae), and Prunus (Rosaceae) (LaBerge 1986). The species has been recorded in deciduous and evergreen forest, shrubland, grassland, agricultural areas, and urban areas. The species nests in loose aggregations in sandy soils (Boyes, Rowntree, and Coulthard 2024), with a foraging distance predicted to be between 300 - 500 m (Greenleaf et al. 2007). However, in a context of land use change, this species may forage from increasing distances from the nest site (Boyes, Rowntree, and Coulthard 2024). This species nests underground like all other Andrena (Danforth et al. 2019). In one examination of Andrena barbilabris nests, tunnels were located on a slope of loose, sandy soil over a layer of more compacted sand (Nieuwenhuijsen. 2020). Nest aggregations can be as large as 1,000 nests (Witt R 1992). 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). In a German study of one large nest aggregation of this species, females were found to make two to three nests each year, with two to three offspring per month (Witt R 1992). Records of this species come from March through September, with most records from April, May, and June (Chesshire et al. 2023; LaBerge 1986). Adults are assumed to emerge annually (Danforth et al. 2019). This species faces high parasitism pressure by Nomia and Sphecodes where this has been directly investigated in Germany (Witt R 1992). Parasite pressure to this species has not been investigated elsewhere in its range.

Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena barbilabris 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 a number of protected land designations across North America and Europe, but occurrences on these lands does not necessarily 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.