Andrena chlorura

Justification:
Andrena chlorura is a dietary generalist bee that occurs in western North America, from southwest Canada to northern Baja California, Mexico, and as far east as Arizona and Utah. Using all observations, the extent of occurrence is 1,509,794 km2. This species has been described as common rangewide, although a localized study has reported it as rare. The species has only been observed one time since 2013, even though there has been substantial search effort within its range in that time period. Across the range of the species, impacts from urbanization, increased wildfire, and exposure to pesticides have been observed. These threats may be acting on the species at local levels. More information is needed to determine if the species is extant throughout its entire historic range, and to determine a population trend for the species. RANK SENTENCE

Andrena chlorura is a dietary generalist bee, and collects pollen from a wide range of spring and early summer blooming shrubs and trees. It may exhibit a preference for plants from the following genera: Salix, Ceanothus, Rhus, and Arctostaphylos (Laberge and Ribble 1975). Andrena chlorura has been recorded as a pollinator of the imperiled plant species Arctostaphylos hookeri ssp. hookeri (Buchmann, Adams, and Howell, A, Weiss, M 2010), and thus may warrant some conservation attention for the role it plays in pollination. It has been recorded in forests, shrublands, agricultural, and urban 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 July, with most observations from March through May (Laberge and Ribble 1975; Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Specific threats to this species have not been investigated. However, it is likely facing threats from climate change and drought, especially in the most arid parts of its range. 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 chlorura 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), 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.