The New Mexico Rare Arthropod Resource

Little is known about the habitats and ecology of this species. The type locality of this species is at about 2,015 m in elevation, in what is likely xeric foothill habitat characterized as a pine-oak woodland. Vegetation types likely include evergreen oaks, alligator junipers and Mexican pines with an understory that is typically comprised of perennial grasses (Wood Miller et al. 2009). This species is likely a specialist on Asteraceae, as nearly all species in this subgenus, Callandrena, are specialists to some degree on pollen of Asteraceae. One of the two collected specimens was taken on cinchweed (Pectis papposa) (Larkin 2004).

This species likely nests in the ground, like other species in the genus Andrena. In most cases, members of this genus make individual nests, sometimes in large aggregations. The nests of most communal species are inhabited by several to many females, and typically have only one entrance, with lateral burrows radiating from the main burrow (Michener 2007). The nest cells, which are at the ends of the lateral burrows, are typically lined with a wax like material, to protect larvae from soil moisture and bacteria (Wilson and Carril 2016). Females fill the bottom of each cell with pollen before inserting a single egg. In most cases, species in the genus Andrena produce only one generation per year, with mature adults overwintering in nest cells. Typically, the two sexes emerge at a similar time the following year (Michener 2007). This species appears to be active in the fall; both known records were taken in the first week of September (Larkin 2004).

This species is known only from the Mimbres Mountains, which comprise the southern portion of the Black Range in southwestern New Mexico. It may be endemic to these mountains, though survey effort in the region is far from extensive. Females of the species have been collected twice, once in 2000 and again in 2002, from the same locality, about 25 miles east of Silver City, Grant County (Larkin 2004).
The extent of occurrence (EOO) and area of occupancy (AOO) could be as low as 4km², as the species is known from just one locality. However, given the lack of survey effort, this is likely underestimated. If the species is found across the Black Range, the EOO could be as much as 5,000 km², and the AOO greater than the 2,000 km² threatened threshold. Until additional occurrences are discovered, the species is considered to be found in one location, where severe catastrophic wildfire is likely the most consequential threat. Continuing decline in quality of habitat due to increasing drought and long term fire suppression practices is inferred.

There are no conservation measures in place for this species. Research is needed to better understand the distribution, population size and trend, habitats and ecology, threats and habitat trends.

The threats to this species are not well understood, though increased wildfire severity and drought due to climate warming are likely threats. The Mimbres Mountains, which comprise the southern portion of the Black Range, is at high risk for catastrophic wildfire. For example, in 2013, a lighting strike near Sawyers Peak, 7.5 km as the crow flies from the type locality of this species, ignited a large wildfire. The fire burned almost 140,000 acres of steep and rugged terrain, ranging from mid-elevation pinyon-juniper scrub to high elevation mixed conifer. While some places within the burn scar were unburned, or burned only moderately, 15% of the area experienced stand replacing fire (US Forest Service 2013). Then again, in 2022, the second largest fire in New Mexico history burned over 325,000 acres of wilderness in the Black Range (Gleason 2022). In other species, such high severity burns result in habitat degradation due to reduction in canopy and organic ground cover across large areas of canyon slopes, direct mortality from fire, and indirect mortality from post-fire erosion or debris flows (Wallace 2021). The incidence of stand replacing fires has increased in the western US, due to climate warming to some extent (Turco et al. 2023) but primarily due to the legacy of forest management practices, which have changed forest structure, resulting in shrub encroachment in mid elevation pine-oak and pinyon-juniper woodland and desert grasslands and closed canopy conditions in the higher elevation conifer forests. For example, an assessment of the Upper Mimbres watershed found 95% of the landscape was moderately or highly departed from historical conditions (Wood Miller 2009).  In the southeastern US, Hanula et al. (2015) found low bee diversity in forests where fire suppression resulted in dense tree stands with high understory shrub cover. Open canopies, with little to no mid-story trees and shrubs and a plant diverse understory are optimal for most bee species.

Climate warming may have other unknown impacts on this species, particularly due to increasing drought conditions. The southwestern U.S. saw its driest 22-year period from 2000 to 2021, since at least 800 CE (the time period used in previous climatic reconstructions) (Williams et al. 2022). Drought may negatively impact bee species by reducing floral resource availability (Phillips et al. 2017). Bees that are oligolectic, like this one, are generally at 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 (Danforth et al. 2019).

While the scope and magnitude of these threats are uncertain, continuing decline in the quality and availability of habitat is inferred. More research is necessary to determine the impacts of these threats on this species. 

The population size and trend are not known for this species. The species has been collected only twice, which suggests it may be quite rare and range restricted, though survey effort has not been extensive.

• Wood Miller, L., Rich, P. and Schumann, M. . 2009. Upper Mimbres Watershed Landscape Assessment. The Nature Conservancy in New Mexico.
• Phillips, B.B., Shaw, R.F., Holland, M.J., Fry, E.L., Bardgett, R.D., Bullock, J.M. and Osborne, J.L.. 2017. Drought reduces floral resources for pollinators. Global Change Biology 24: (3226-3235).
• Gleason, M.. 2022. After burning over 325,000 acres of Gila wilderness, the Black Fire is mostly out. Source New Mexico . https://sourcenm.com/2022/07/27/after-burning-over-325000-acres-of-gila-wilderness-the-black-fire-is-mostly-out/
• Turco, M., Abatzoglou, J.T. , Herrera, S., Zhuang, Y., Jerez, S., Lucas, D.D., AghaKouchak, A. and Cvijanovic, I.. 2023. Anthropogenic climate change impacts exacerbate summer forest fires in California. PNAS 120: (e2213815120).
• Hanula, J.L., Horn, S. and O'Brien, J.J.. 2015. Have changing forests conditions contributed to pollinator decline in the southeastern United States?. Forest Ecology and Management 348: (142-152).
• Michener, D.C.. 2007. The Bees of the World. The Johns Hopkins University Press, Baltimore : (953).
• ITIS. 2024. Integrated Taxonomic Information System (ITIS). 2024. https://www.itis.gov/
• Wallace, J.E.. 2021. Status and Distribution of Terrestrial Snails in Southwestern New Mexico. Final Report to: New Mexico Department of Game and Fish Share with Wildlife Program , Tucson, AZ .
• Larkin, L.L.. 2004. Four New Fall Species of Andrena from the Southwestern United States (Hymenoptera: Andrenidae). Journal of the Kansas Entomological Society 77: (254-268).
• Danforth, B. N., Mincley, R. L., Neff, J. L., and Fawcett, F.. 2019. The solitary bees: biology, evolution, conservation. Princeton University Press.
• Packer, L., Zayed, A., Grixti, J.C., Ruz, L., Owen, R.E., Vivallo, F. and Toro, H.. 2005. Conservation genetics of potentially endangered mutualisms: reduced levels of genetic variation in specialist versus generalist bees. Conservation Biology 19: (195-202).
• Wilson, J.S. and Carril, O.M. 2016. The Bees in Your Backyard: A Guide to North America's Bees. Princeton University Press, Princeton, NJ .
• Williams, A.P., Cook, B.I. and Smerdon, J.E. . 2022. Rapid intensification of the emerging southwestern North American megadrought in 2020–2021. Nature Climate Change 12: (232-234).
• USGCRP. 2018. Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II. U.S. Global Change Research Program , Washington, DC, USA : (1515).
• Roberts, S.P.M., Potts, S.G., Biesmeijer, K., Kuhlmann, M., Kunin, B. and Ohlemüller, R.. 2011. Assessing continental-scale risks for generalist and specialist pollinating bee species under climate change. BioRisk 6: (18-Jan).
• US Forest Service. 2013. Burned Area Emergency Response (BAER) Team Executive Summary. Black Range, Silver City, and Wilderness Ranger Districts Gila National Forest, Silver City, NM : (13).