Diversity of wild bees in wet meadows: Implications for conservation

Abstract

Substantial industrial development, agricultural intensification, and an increasing human population have led to the demise of many seminatural habitats, such as wet meadows, in many countries of Europe. This process can cause the extinction and decline of associated insect species. The present paper is the first study analyzing wild bee diversity and abundance patterns in wet meadows. We surveyed bees using pan traps, transect walks, and nest traps in four Molinietum (Poaceae) meadows near Kraków, Poland. During one season, we identified a relatively high γ-diversity of wild bees, consisting of 105 species (13 from the Polish Red List) belonging to 22 genera, which represent almost one-fourth of the Polish bees. The wild bee fauna between sites was not variable, which was indicated by low ß-diversity. We found that nesting preference of bees did not differ between the study area and xerothermic meadows, which suggests that differentiation in bee fauna of wet and dry grasslands is mostly due to food specialization rather than nesting preference. Abundance analysis of the bee community showed that the least abundant species were disproportionately comprised of oligolectic species, indicating that species closely associated to plants of wet meadows are especially threatened. Moreover, using occurrence data we found that 34% of the species belonging to the families Halictidae, Melittidae, and the tribe Nomadini found in wet meadows are considered rare in Poland. Our results highlight an urgent need to perform further investigations and develop specific protection plans for bees not only in Kraków’s Molinietum meadows, but also in wetlands throughout Europe.