Andrena camissoniae

Justification:
Andrena camissoniae is a solitary bee species known from just three individuals from three localities. It occurs in the foothills of California’s Coast Range, United States. Using all known observations of this species, the extent of occurrence is 5,002 km2, and the area of occurrence is 12 km2. Both of these metrics are likely underestimated due to limits to data availability, including search effort, species identification, and data digitization. The species has not been observed since 1963, and it is unclear if it is still extant. Andrena camissoniae occurs in California coastal sage scrub, which is a habitat that has faced threats from habitat loss, degradation, and fragmentation due to exceptionally high development pressure, grassland conversion due to exotic grass invasion and subsequent fire regime change, and climate change. Based on these threats, continuing decline in habitat quality is inferred. The three known localities may represent three locations if the threats observed in this habitat type act on each locality separately. Due to the small extent of occurrence, limited potential number of localities, and ongoing decline in habitat quality, this species is assessed as Vulnerable under criterion B1ab(iii). However, more information is urgently needed to determine if this species is still extant throughout its range, and to determine if a higher threat category is appropriate.

Distribution

Population

Habitats and Ecology

There is little available information about this species. It has been recorded foraging from Camissonia campestris (Onagraceae), but there are too few records to determine dietary breadth. It has been recorded in grasslands and shrublands of the central California foothills of the Coast Range. 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 June (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Habitat Types

Use and Trade

Threats

This species occurs in California coastal sage scrub habitat, one of California's most threatened vegetation types, which is globally imperiled (NatureServe 2024). This habitat is highly threatened by modification, fragmentation, and loss due to urban and suburban growth. Nearly half of California’s residents live in the coastal California counties where this habitat occurs, which is less than 10% of the state’s land area (Riordan and Rundel 2013). Less than 20% of this habitat remains (Davis, Stine, and Stoms 1994), and the existing fragments are considered some of most valuable real estate in California. This contributes to considerable development pressure on remaining fragments, and their high real estate value makes their conservation costly. Coastal sage scrub has also been modified significantly in the past 100 years due to exotic annual grass invasion, which has been facilitated by increased wildfire frequency (Minnich and Dezzani 1998; Talluto and Suding 2008). These factors also contribute to a feedback where increased grass cover increases fire frequency, leading to grassland conversion. This habitat conversion may limit the availability of host plants used by Andrena camissoniae and alter other abiotic factors important for this species. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena camissoniae 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).

Conservation Actions

Conservation needs No known conservation actions are in place for this species. Observations of this species are known from Bureau of Land Management (BLM) and US Forest 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. 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
7	Natural system modifications - 7.1. Fire & fire suppression -> 7.1.2. Suppression in fire frequency/intensity	Ongoing	Minority (<50%)	Slow, significant declines
7.1.1	Natural system modifications - Increase in fire frequency/intensity	Ongoing	Minority (<50%)	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