Andrena tegularis

Justification:
Andrena tegularis is a solitary bee species that occurs in the southwestern United States (Arizona State), and in the Sierra Madre Occidental of Western Mexico. It is known from only approximately 60 observations. Using all observations, the extent of occurrence for the species is 535,486 km2. Recent records (since 2013) come from northern Arizona and central Mexico. There is little information about the habitat and ecology of this species. Records come from mid- to high-elevation mixed and coniferous forest. Across the range of the species, threats from climate change, drought, and deforestation have been observed, and may be acting on the species at local levels. More information is needed to determine the impact of these threats, understand the population status, and to document more life history of the species. Because the species is widespread and occurs in several different habitat types, it is unlikely that it is threatened with extinction at this time. As such, it is assessed as Least Concern for now.

Andrena tegularis is a solitary bee species that has been recorded in mid- to high-elevation sites in mixed and coniferous forests of the mountains of the Sky Island Region and the Sierra Madre Occidental. There is little available information about the dietary breadth of this species. It has been recorded from Heliopsis (Asteraceae) (LaBerge, 1967). 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 & 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 July through October, but chiefly from September (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 et al., 2022). Drought can reduce the abundance of flowering plants on a landscape scale, and also reduce pollen and nectar quality (Wilson Rankin et al., 2020). Drought conditions have been shown to reduce the diversity and abundance of native bees (Hung et al., 2021; Minckley et al., 2013). Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena tegularis 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 may be 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 & Paxton, 2009; Grab et al., 2019; Potts et al., 2010; Raven & Wagner, 2021; Wojcik et al., 2018).

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