Identification of a previously overlooked anthropogenic habitat that attracts diverse assemblages of threatened bees and wasps
Abstract
The extent of anthropogenic habitats that support species-rich assemblages of bees and wasps is poorly understood. In the present study, we identified a previously overlooked hotspot of bee and wasp (Hymenoptera: Aculeata) biodiversity that consists of bare loess exposed by anthropogenic activities, mostly in clay pits but also in slopes of sunken lanes or upper berms of sand pits.
We examined the diversity of bees and wasps in microhabitats with exposed bare loess at 17 sampling sites, which were located throughout the Czech Republic. Using color pan traps and metal-roof-bearing pitfall traps, we identified 328 species of bees and wasps, of which 61 were threatened.
The threatened species were dominated by specialists for loessic, sandy and steppic habitats but included also several wetland specialists. The examined assemblages were rich in threatened polylectic pollinators and threatened predators of Lepidoptera, Araneae, Diptera and Auchenorrhyncha.
The present oligolectic pollinators were mostly specialists for Asteraceae, Fabaceae and Rosaceae. Importantly, the spectrum of species found overlapped only partly with those identified previously in other anthropogenic habitats, and 83 species, of which 35 were considered threatened, were absent from the compared studies at all.
The two capture methods used generated different results; color pan traps were dominated by polylectic pollinators, whereas the pitfall traps attracted multiple predatory species. The analyzed assemblages of aculeate hymenopterans were characterized by their low dominance (1-Simpson index 0.066) and high alpha diversity (Fisher's alpha 66.4).
We concluded that bare loess exposed by anthropogenic activities allows the formation of species-rich assemblages of aculeate hymenopterans, which include numerous species that become rare in cultural landscapes.