Tiny fragments of acidophilous steppic grasslands serve as yet unknown habitats of endangered aeolian sand specialists among Aculeata (Hymenoptera)

Aeolian sand specialists are traditionally recognized among the most threatened species of central European landscapes due to habitat loss. In the present study, we examined the diversity of bees and wasps, and the cover and composition of vegetation in 17 neglected small fragments of Artemisio campestris–Corynephoretum canescentis acidophilous grasslands, which developed on weathered granodiorite rocks in the Czech Republic. The size of the examined fragments ranged from 128 to 14,000 m², with a total area of only 5.7 ha. At the examined sites, we identified species-rich assemblages of endangered aculeate hymenopterans that were previously thought to be specialized on aeolian sands. We found that despite the small area and relative isolation of the examined sites, they hosted 26 Red-Listed species of bees and wasps and a species new to Bohemia (Megachile pilicrus), respectively. The examined habitats also supported the presence of 18 Red-Listed receding field weeds and steppic grassland specialists. The analyzed bee and wasp assemblages were characterized by their low dominance (1-Simpson index = 0.091) and high alpha diversity (Fisher’s alpha = 48.9). Although the examined fragments of acidophilous steppic grasslands differed in size by two orders of magnitude, the total abundance and species richness of the bees and wasps were not correlated with the size of the fragments. This suggests the long-term stability despite the minute size of some of the residual fragments. Land protection and active management are proposed to conserve these habitats for future generations.