Asymmetric responses by bees and aculeate wasps to dune stabilisation across the southern Canadian prairies

Abstract

Abstract Inland sand dunes in the Great Plains of North America provide refuge for a variety of psammophilous (i.e., sand‐loving) organisms but are threatened by vegetative stabilisation. In a cross‐sectional study, we analysed the effects of dune stabilisation on wild bees and stinging wasps (Hymenoptera: Aculeata)—which comprise some of the most diverse assemblages of dune‐dwelling arthropods—at 13 sites across the southern Canadian prairies. We did not detect changes in overall taxonomic richness with increased stabilisation, with comparable numbers of bee and aculeate wasp species/morphospecies observed among dunes at different stages of stabilisation. However, abundances of species of wasps identified as dune specialists decreased with increased stabilisation. Bees and aculeate wasps responded nonlinearly to the percent of plant cover on dunes dominated by grasses (Poales: Poaceae), whereas abundance and richness were generally high on dunes where the dominant plant was dune scurfpea (Fabales: Fabaceae). Thus, the extent to which these plants cover a particular dune can be indicative of the numbers of individuals and types of aculeate species it can sustain. Overall, differences in aculeate community composition between dune sites were better explained by proximity of sites to one another than stabilisation level, reflecting the large spatial scale at which the dunes were surveyed (i.e., within a 50,350 km2 area). Bees and aculeate wasps, especially open sand specialist species, serve as a promising tool for monitoring the effects of dune stabilisation. This study provides a crucial reference point and methodology for future assessments of dune‐inhabiting aculeates in these unique inland dune systems.