Andrena crinita

Justification:
Andrena crinita is a solitary bee species known from approximately 10 observations, and occurs in mountainous northern Arizona, United States. There is little information available about the life history of this species, including dietary breadth, as most records are from pan traps, and no other records include floral associations. Using all records of the species, the extent of occurrence (EOO), is 8,087 km2, and it is known from just 5 localities. Although the species meets the criteria to be considered as Vulnerable based Criterion B2, and (b) continuing decline estimated in (v) number of mature individuals, nearly all localities of this species come from protected areas, where it does not face threats from habitat loss or direct exposure to pesticides. It is unclear if there are threats substantial enough to consider localities as locations. The species is likely threatened by climate change at all of its localities, but without additional information about its life history, it is unclear how climate change will affect the species. More information about the range limits, dietary breadth, population size and trend, and threats is needed for this species. For now, this species is assessed as Data Deficient, although should it be confirmed as occurring at few locations based on threat information, it should be reassessed as Vulnerable.

Distribution

Population

Habitats and Ecology

There is little available information about the habitat and ecology of this Andrena crinita. Of the 11 available records of this species, seven were collected by bowl or pan trap (McCabe et al. 2020), so there are no associated floral records. The remaining records are not accompanied by sampling protocol or associated floral resource data, thus the dietary breadth of this species is unknown. The records accompanied by the most comprehensive associated data (McCabe et al. 2020), were collected in well established, healthy mixed ponderosa pine (Pinus ponderosa), and Aspen (Populus tremuloides) forest of the EPA level III ecoregion Arizona/New Mexico Mountains (L. McCabe, pers. comm. with S. Killingsworth 11 Dec 2024). Other records come from mixed shrubland of the Central Basin and Range, and conifer forest of the Arizona/New Mexico Mountains. 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 through July (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Habitat Types

Use and Trade

Threats

In the study that has produced the majority of the records of this species (McCabe et al. 2020), this species was detected multiple times in the first half of the study, but not at all the in the later years of the study, despite no apparent decline in habitat quality, reduction of floral resources, or obvious threats to bees (L. McCabe, pers. comm. with S. Killingsworth 11 Dec 2024). There may be some threat impacting the year to year population of this species that has not yet been detected, or some element of its natural history that contributes to limited emergence in some years that is not well understood. Overall the region in which this species occurs 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). Climate change, including increased temperatures, may impact the habitat quality of this species. Observations of Andrena crinita come from some of the highest elevation habitat in Arizona (McCabe et al. 2020), with limited available upslope habitat in the surrounding vicinity. Should climate change alter the habitat at the elevation where this species occurs, it is unclear if the limited upslope habitat would be suitable, and if the species would be able to migrate there. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena crinita 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 Actions

Conservation needs No known conservation actions are in place for this species, however nearly all observations of this species are from protected lands. Records come from United States Forest Service 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. 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
7	Natural system modifications - 7.1. Fire & fire suppression -> 7.1.2. Suppression in fire frequency/intensity	Ongoing	Minority (<50%)	Slow, significant declines
7.1.2	Natural system modifications - 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
11	Climate change & severe weather - 11.3.Temperature extremes	Ongoing	Majority (50-90%)	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	Majority (50-90%)	Slow, significant declines
11.3	Climate change & severe weather - Temperature extremes	Ongoing	Majority (50-90%)	Slow, significant declines

Assessment