Andrena barberi

Justification:
Andrena barberi is a solitary bee that visits plants from the family Asteraceae for pollen. It occurs throughout Mexico, mostly in higher elevation oak and pine forest, as well as in western Guatemala and southwest United States. Using all records, the extent of occurrence for this species is 1,350,308 km2. Recent observations come from several widely dispersed localities in Mexico. The species has not been recently observed in the United States, and it is unclear if the species still persists there. Across the range of the species, impacts from climate change, agricultural conversion, illegal logging, and other habitat loss have been observed, and may be acting on the species at local levels. However, because the species is widespread, occurs in several different habitat types, and because its host plants are likely abundant and widespread, it is unlikely that the species is threatened with extinction at this time. As such, it is assessed as Data Deficient for now.

Floral records associated with Andrena barberi suggest that the species may be a dietary specialist, visiting flowers from the family Asteraceae for pollen (LaBerge 1967). Asteraceae genera associated with this bee include Bidens, Heterotheca, Rudbeckia, and Solidago. This species has been recorded in the pine-oak forests of the Sierra Madre Occidental range, and the trans-Mexican volcanic belt pine-oak forests of Mexico, and Central American pine-oak forests. 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 June through November, but mostly from August (LaBerge 1967; Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Since 2000, the Southwest U.S. 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 (Minckley, Roulston, and Williams 2013; Hung et al. 2021). There has been significant agricultural expansion throughout the Sierra Madre Occidental, Mexico in recent years (Bonilla-Moheno and Aide 2020). Additionally, illegal logging in the region has increased in the last several decades (García-Jiménez and Vargas-Rodriguez 2021). These major land use changes may be reducing habitat essential to Andrena barberi. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena barberi 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 a dietary specialist, 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).

Conservation needs No known conservation actions are in place for this species. Observations of this species are known from United States Forest Service land in the United States, and federally protected land in Mexico, 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.