Andrena cymatilis

Justification:
Andrena cymatilis is a solitary bee known from few observations. It occurs in the western United States, from southern Oregon south to central California. Using all observations of the species, the extent of occurrence is 63,982 km2. Using all observations of the species the area of occurrence is 32 km2. The persistence of this species throughout its range is not well understood. The most recent observations come from bee fauna studies with vague locality data and imprecise date data. Aside from these three observations (1995 - 2011), the species has not been observed since 1974. There is little available information about the habitat and ecology of this species. It appears to forage from species of Blennosperma, one of which is a federally endangered species. It occurs in grasslands and shrublands, and may also occur in California’s rare vernal pool ecosystem. Across the range of the species, impacts from habitat loss, fragmentation, and degradation have been observed due to urbanization. This species may also be impacted by climate change and exposure to pesticides. This species is known from eight localities, contributing to a total of eight locations for this species if threats act on each locality independently. More information is needed to determine if this species still persists throughout its range, and to better understand its life history. Although this species qualifies for an imperiled ranking based on its small AOO, low number of locations, and observed decline in habitat quality, the AOO is likely underestimated due to limited sampling effort for bees. It is instead evaluated here as Near Threatened, based on its extent of occurrence.

Distribution

Population

Habitats and Ecology

Food habits comment: There is very little information about the habitat and ecology of Andrena cymatilis. It has been recorded in association with federally endangered Blennosperma bakeri (Gilmore 2018). It has also been recorded foraging on Blennosperma nanna (LaBerge 1986). Habitat comment: This species has been recorded in shrublands and grasslands, between 14 and 1,294 m. Reproduction comment: 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). Phenology comment: Records of this species come from March through May (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Habitat Types

Use and Trade

Threats

Threat comments: Specific threats to this species have not been directly studied, and there is little information available about the habitat and ecology of this species, which make assessment of threats more meaningful. This species has been recorded in association with California vernal pool obligate species. If this bee requires vernal pool habitat, it faces threats due to the degradation, fragmentation, and loss of its habitat. These habitats are made up of discrete, ephemeral wetlands, and are characterized by their impervious substrate that collects winter precipitation that dries out over the course of the summer (Holland 2009). In California, the Central Valley vernal pool ecosystem has declined 95% from its historic extent (Dahl 1990). Much of the remaining vernal pool habitat occurs in areas with high pressure from urbanization and agricultural expansion, which is expected to continue. Vernal pool habitat is also threatened by alteration of hydrology, which can happen either through droughts, which are predicted to become more frequent and severe across the range of the species (Franklin and MacDonald 2024), or via increased irrigation with reclaimed water. In some sites where the host plant occurs, increased water in vernal pool sites has occurred via agricultural runoff. Increased water or irrigation at the wrong time of year can kill host plants, and can contain pollutants such as herbicide and excess nutrients, which can kill host plants and encourage invasion of exotic species (USFWS 2016). Urbanization and irrigation with recycled water has contributed to at least two locality extirpations of Blennosperma bakeri (USFWS 2016), which may be an important food plant for the species. This ecosystem Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena cymatilis 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 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 and Paxton 2009; Potts et al. 2010; Wojcik et al. 2018; Grab et al. 2019; Raven and Wagner 2021). Threats Threats:

Conservation Actions

Conservation needs No known conservation actions are in place for this species. Protected/Managed area comment: Observations of this species are known from United States Forest Service land, but this does not confer any specific protections to the species. Management comment: 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.

Code	Threat	Timing	Scope	Severity
1	Residential & commercial development - 1.2. Commercial & industrial areas	Ongoing	Majority (50-90%)	Slow, significant declines
1.1	Residential & commercial development - Housing & urban areas	Ongoing	Majority (50-90%)	Slow, significant declines
1.2	Residential & commercial development - Commercial & industrial areas	Ongoing	Majority (50-90%)	Slow, significant declines
8	Invasive and other problematic species, genes, and diseases - 8.1 Invasive non-native/alien species/diseases -> 8.1.2. Named species	Ongoing	Minority (<50%)	Slow, significant declines
8.1.2	Invasive and other problematic species, genes, and diseases - Named species	Ongoing	Minority (<50%)	Slow, significant declines
9	Pollution - 9.3 Agricultural and forestry effluents -> 9.3.3 Herbicides and Pesticides	Ongoing	Minority (<50%)	Slow, significant declines
9.3.3	Pollution - Herbicides and Pesticides	Ongoing	Minority (<50%)	Slow, significant declines
11	Climate change & severe weather - 11.3.Temperature extremes	Ongoing	Minority (<50%)	Slow, significant declines
11.1	Climate change & severe weather - Habitat shifting & alteration	Ongoing	Majority (50-90%)	Slow, significant declines
11.2	Climate change & severe weather - Droughts	Ongoing	Minority (<50%)	Slow, significant declines
11.3	Climate change & severe weather - Temperature extremes	Ongoing	Minority (<50%)	Slow, significant declines

Assessment