Land cover composition, local plant community composition and honeybee colony density affect wild bee species assemblages in a Mediterranean biodiversity hot-spot

Abstract

Identifying environmental drivers which structure wild bee species assemblages appears essential in a context of worldwide pollinator decline. During a two-year survey, we studied wild bee species assemblages in an 85km2 protected area dominated by Mediterranean scrubland, the Calanques National Park, located in southern France. Our objectives were (i) to assess the composition of the wild bee species assemblages, and (ii) to explore the effect of a) land cover composition (anthropogenic zone, low scrubland, forest and rocky land cover), b) local plant community composition, and c) honeybee colony density on wild bee species assemblages. On 17 circular 100m2 plots, we collected 541 specimens belonging to 87 wild bee species. We found that large bee species were significantly influenced by land cover composition within a 1000m radius. More specifically, we observed that the presence of a diversified land cover composition within a 1000m radius maximized large wild bee species richness, whereas large bee abundance and richness were negatively affected by honeybee colony density. Small wild bee species were structured by the local plant community composition within 100m2 plots and by land cover composition within a 1000m radius. Their occurrence were related to the local composition of plants growing on deep soils in scrublands. The Calanques National Park, which is the only European park located at the interface with a large city and consequently suffers from anthropic pressure, encompasses several types of land cover which are beneficial for a wide diversity of bees. However, we would like to raise awareness among park managers regarding beekeeping activities within this territory which includes diverse types of land cover favorable for wild bee species.