Andrena buccata

Justification:
Andrena buccata is a solitary bee species known from 15 observations. It occurs in central California. Using all observations, the extent of occurrence (EOO) is 33,108 km2, however the species has not been observed since 1976, and it is not clear if the species is still extant. Across the range of the species, impacts from climate change and drought, habitat degradation and loss due to agricultural expansion and urbanization, and exposure to pesticides have been observed. These threats may be acting on the species at local levels. It is known from just 13 localities, and may occur in just 13 locations if threats act on each locality independently. More information is urgently needed to determine if this species is still extant, and if it is, to better understand its range, habitat needs, population trends, and threats. Because it is known from a relatively small EOO, few locations, and ongoing decline in habitat quality can be inferred, this species is assessed as Near Threatened for now.

The dietary breadth of this species is not well understood due to limited records. It has been recorded from Platystemon (Papaveraceae), and Lasthenia and Blennospermata (Asteraceae) (Laberge 1971). In a study of the reproductive biology of Platystemon californicus, four Andrena buccata specimens were collected from Platystemon at two different sites. All of these specimens were carrying over 95% Platystemon pollen (Hannan 1981), suggesting that the plant may be important to the diet of the bee. The bee has been recorded in grasslands, shrublands, evergreen forests, and urban 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). Records of this species come from March and April (Chesshire et al. 2023; Laberge 1971). Adults are assumed to emerge annually (Danforth et al. 2019).

Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena buccata 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). 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) land. It has also been recorded from the Pleasanton Ridge Regional Park, the Bear Valley Conservation Area, and private land. None of these land holdings provide any conservation measures to address the needs of this bee. 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.