Hymenopteran groups' role in ecological indication along the last traditionally managed meadows in Eastern Europe

Abstract

Abstract During this research, the role of wild bees and cavity-nesting Hymenopteran species as indicators was examined, along the unique combination of high nature value and traditional land use habitats. We encountered a high diversity of wild bees was detected, but also a significant species replacement from one study year to another. Among the nests building species, Trypoxylon sp. showed a considerably stronger dominance in the second year (72.23% of all nests), which may be due to changes in spider prey densities. The number of nests built by the two solitary bee taxa Megachile and Osmia also increased for the second year of our study. There are several possible explanations for these differences, one of which could be a considerable change in temperature between the two years, or the effect of possible competition with honeybees. The different taxonomic groups of wild bees and cavity-nesting Hymenopterans showed differences in their habitat affinities. The majority of the sampled bumblebee species had an affinity towards the sampling sites located within the highly protected areas. In contrast to this, the three groups of more common solitary bees (Andrena, Halictus and Lasioglossum spp.) mostly showed stronger affinities towards the less protected and thus more human-influenced sampling areas. In addition, we registered that landscape structure had no significant effects on the number of (occupied) brood cells for most of the cavity-nesting Hymenopteran groups. From these groups, landscape structure had the clearest effect on the nests built by the wasp Trypoxylon sp., especially when looking at the data from both study years together. Altogether, we can conclude that different habitat preferences of Hymenopteran groups can be detected in these rare semi-natural landscapes. However, in future studies several other factors have to be tested to see the whole picture in these preferences. As only few such habitats still remain in Europe and as the maintenance of insect biodiversity is crucial for well-functioning ecosystems, our results can be important for future researches in areas both less or more strongly influenced by humans.