Andrena antonitonis

Justification:
Andrena antonitonis is a solitary bee species known from a single observation from 1899. It was observed in Antonito, Colorado, United States. Because there is only one observation, an extent of occurrence was not calculated. The area of occurrence for this species is 4 km2, and the species is known from just one location, defined by the threat of exposure to pesticides due to the proximity of alfalfa and non-alfalfa hay production. The area surrounding the locality of this species also faces high vulnerability to land use change in the next 50 years. It is unclear if this species is still extant. More information is needed to determine if this species still occurs in the area, and to describe its life history, threats, and population status. This species should be looked for in unidentified museum materials. Because this species has an extremely small AOO, is known from just one location, and surrounding habitat faces a projected decline in habitat extent and quality, it is ranked as Critically Endangered for now.

There is no available information about the habitat and ecology of this species. A precise location for the single observation of this species is not available, but the vicinity of the existing geolocation of the record is made up of shrubland, residential areas, and agricultural 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). The record of this species comes from May (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

The only existing record of this species is located in an area that has high vulnerability to land cover change (Clark Lab & Esri 2020). Additionally, the locality is in proximity to agricultural lands, mostly alfalfa and non-alfalfa hay, both of which are high pesticide input crops. Exposure to pesticides used in these crops causes lethal and sublethal impacts for this species. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena antonitonis is likely 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. 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.