Andrena helianthi

Justification:
The sunflower mining bee is a widespread pollen specialist bee that occurs across much of the United States and the southern part of Canada. Using all known records of the species, the extent of occurrence (EOO) is 6,331,467 km2. Although it is a narrow pollen specialist of the genus Helianthus (Asteraceae), its host plants are widespread, abundant, and occur in a variety of habitats. The species is an important pollinator of confection sunflower crops, and thus can utilize agricultural landscapes, although this may come with increased exposure to pesticides. Within the range of this species, major land use change, resulting in habitat fragmentation, loss, and degradation have occurred, coupled with increased use of pesticides. These threats may be acting on the species at a local scale. More research is needed to describe population trends and threats. Because this species is widespread and occurs in many different ecoregions, it is unlikely that it is threatened with extinction at this time. As such, it is assessed as Least Concern.

The sunflower mining bee is a widespread, pollen specialist bee species that uses pollen from the plant family Asteraceae, in particular, the genus Helianthus (LaBerge 1967). The species is one of the most effective pollinators of confection sunflower crops, making them an economically important species (Mallinger et al. 2019). The bee collects pollen by rubbing the curled over tip of its abdomen against the anthers of the sunflower, and periodically scraping the abdomen with the hind leg scopae to transfer the accumulated pollen (Portman, Orr, and Griswold 2019). This widespread species occurs in many different habitat types, including the arid shrublands, grasslands, and deserts of the southwest US, mid-elevation forests and foothills of the Rocky Mountains, grasslands of the Great Plains, and hardwood forests of the Great Lakes region and northeast US. Andrena nests are located at the lateral ends of underground burrows. Nests of this species have been described from a sunflower field near Logan, Utah (Parker and Bohart 1982). Nests were located between irrigation furrows in silty loam, with entrances usually near sunflower stalks. Most nests were spaced a meter or more apart, but some were as close as a couple of centimeters. The main burrows of these nests were plugged with soil at various intervals, blocking off access to nest cells located deeper. Cells were located around 40 cm deep, and in a short series of 1-3 cells. Cells per nest ranged from 1 - 8, averaging 4.2. The basal ⅔ of the cell was lined with a smooth, brown layer of 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). Parasitic bees from the genus Nomada were observed within the nests of the sunflower mining bee (Parker and Bohart 1982). Females provision each cell with a ball of pollen moistened with nectar on which they lay a single egg (Michener 2007). Foraging is most active in the morning through midday, and tapers off by early afternoon. Records of this species come from July through September (Parker and Bohart 1982; Chesshire et al. 2023). This species is presumed to have only one generation a year (Parker and Bohart 1982). Adults are assumed to emerge annually (Danforth et al. 2019). * 1.4. Forest – Temperate * 3.4. Shrubland –Temperate * 4.4. Grassland – Temperate * 8.2. Desert – Temperate * 14.1 Arable Land * 14.5 Urban Areas

Threats to this species are not well understood. This species may be threatened by decreased or highly variable floral resource availability due to drought in parts of its range.Since 2000, the Southwest U.S. has seen the worst drought in 1200 years (A. P. 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). Additionally, the native grasslands in the Midwest United States where this bee occurs have seen major impacts due to agricultural intensification and expansion (Foley et al. 2005). These changes have resulted in a loss of intact prairie ecosystems, as well as a decline in overall habitat quality and available forage (Samson and Knopf 1994; Samson, Knopf, and Ostlie 2004; Otto et al. 2018). Land use conversion to agriculture also comes with increased pesticide exposure for the sunflower miner bee, which may contribute to serious risk for this species. Although the dietary needs of this species may be met by sunflower (Helianthus) farming, the associated risks of pesticide exposure and nest site disturbance through tillings may contribute to overall habitat unsuitability for the species. Certain aspects of this species' biology may make it more vulnerable to some threats. Andrena helianthi 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 (N. M. Williams et al. 2010). This species is oligolectic, 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). This species has had its conservation status evaluated using NatureServe criteria at the U.S. state and Canadian province level in some areas where it occurs. It has been evaluated as Vulnerable in Ontario, Canada, and Indiana, U.S., and Critically Imperiled in New York and Connecticut.

No known conservation actions are in place for this species. Observations of this species are known from Bureau of Land Management (BLM), United States Forest Service, United States Fish and Wildlife, and National Park 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 better understand 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.

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