Andrena ceanothifloris

Justification:
Andrena ceanothifloris is a dietary specialist bee that collects pollen from the plant family Rhamnaceae. It occurs in the forests and shrublands of the western United States and southwestern Canada. Using all verified observations, the extent of occurrence for this species is 1,468,080 km2. The species has not been observed since 2004, despite over six times as much search effort within its range as was historically required to detect it. It is unclear if this species is still extant throughout its extent of occurrence. Across the range of the species, impacts from urbanization, climate change, and exposure to pesticides have been observed. These may be acting on the species at local levels. More information is needed to determine if this species is truly absent from its range, and the degree to which threats are impacting this species. As such it is assessed as RANK.

Andrena ceanothifloris is a dietary specialist species that collects pollen from plants in the genus Ceanothus (Rhamnaceae). It occurs in the forests and shrublands of the Mountain West of the United States and southern Canada. 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 April through August, with most observations from June and July (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Specific threats to this species are not well understood. Part of the range of this species has been subject to major drought that may be impacting the quality of habitat and availability of resources. 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 ceanothifloris 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). 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 Bureau of Land Management (BLM), United States Forest Service, United States Fish and Wildlife, 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. This species has been ranked by the New York State Heritage program as Extirpated in New York using NatureServe criteria (CITE). However, all New York records are thought to be erroneous (J. Ascher, pers. comm. with S. Killingsworth 20 July 2024). 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.