Andrena helianthiformis

Justification:
Andrena helianthiformis is a solitary bee that is known from approximately 75 observations. It occurs in the central United States, from Oklahoma north to Kansas and Missouri and northwest to Nebraska and North and South Dakota. Using all observations of the species, the extent of occurrence (EOO) is 736,317 km2. There are some additional records with vague locality data that would extend the size of the EOO. The EOO reported here is likely underestimated. This species is a dietary specialist, using pollen from the Asteraceae tribe Helianthae, possibly further restricted to the genus Echinacea. It occurs in grasslands and prairies, which have seen dramatic habitat loss and degradation due to agricultural conversion in the last two centuries. This contributes to change in abundance of host plants and impacts from habitat fragmentation. This species may also be subject to exposure to pesticides and climate change. More information is needed to understand the population status of the species, and the degree to which threats are acting on the population. IUCN rank justification paragraph

Food habits comment: Andrena helianthiformis is a dietary specialist, that collects pollen from the Asteraceae tribe Heliantheae (Larkin, Neff, and Simpson 2008). It may be further restricted to foraging from within the plant genus Echinacea (LaBerge 1967). Habitat comment: This species has been recorded in grasslands and prairies, between 177 and 1,652 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 June and July (Chesshire et al. 2023). Adults are assumed to emerge annually (Danforth et al. 2019).

Threat comments: Specific threats to this species have not been directly investigated. It is impacted by habitat loss and degradation. This species occurs in the Great Plains region of the United States, a landscape that has seen major habitat loss and modification in the last 200 years (Samson and Knopf 1994). Much of this modification has resulted from agricultural conversion, which has both altered the plant community composition, and increased the potential for exposure to pesticides at levels lethal for bees. The remaining prairie ecosystem within the range of the species is made up by habitat fragments of varying size. Habitat loss due to fragmentation and also increased habitat disturbance via roads have been shown to negatively influence bee abundance in prairie ecosystems (Olynyk, Westwood, and Koper 2021). Fragmentation can also decrease plant diversity, contributing to reduced bee abundance (Winfree et al. 2009; Glaum et al. 2017; Theodorou et al. 2020). Lack of connectivity between habitat fragments can contribute to reduced genetic diversity, as bees may not be able to travel between habitat fragments to mate (Tscharntke et al. 2005). Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena helianthiformis 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 is 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 needs No known conservation actions are in place for this species. Protected/Managed area comment: Observations of this species are known from National Park Service and 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.

Research need comment: More information is needed about the population status, population trend, existing threats, range limits, habitat, and ecology of this species. Surveys targeting this species are needed throughout its range to determine its persistence throughout its historic range.

(a. any taxonomic concerns about the validity of the species? b. any taxonomic revisions underway that would require a species reassessment.