Impact of inundation regime and meadow management on wild bee communities and bee-flower networks in the National Park Donau-Auen
Neumüller Ulrich, University of Vienna (AT)
Inundation events are a major factor shaping insect communities on riverine meadows. In this study bee communities on almost annually flooded meadows were compared with communities on rarely inundated meadows. Flower-visiting bees were sampled on 32 meadows in the National Park Donau-Auen between late April and early August 2016. Sixteen meadows were situated on the flood-prone and another 16 on the protected side of a levee. Altogether, 92 wild bee species interacting with 62 plant species were recorded. Mowing activities and abundance of feeding plants were main drivers altering wild bee activity density and diversity. Counter to expectations, flooding regime had no significant impact on observed individual numbers. Rather, on regularly flooded meadows a higher species richness was found. As a potential driver of this pattern, an increased bee differentiation diversity on annually flooded meadows could be identified. To obtain further insight into the functional characteristics of the bee communities, three network metrics, derived from a bipartite plant-bee interaction matrix were analyzed. None of the network indices was affected by the flooding regime. Hence it is concluded that floods initially may have a devastating effect on wild bee populations, but stable communities are restored in a rather short time. The observed resilience surely depends on the surrounding landscape. Hence it is important, in this region, to consider biodiversity on a landscape comprising scale.