Beaver wetlands create a buzz and a flutter for pollinators

Abstract

1. Beavers are second only to humans in their capacity to transform landscapes. Biodiversity responses to their habitat engineering activities are well studied but rarely so ‘beyond the pond’ despite habitat alteration commonly extending into more terrestrial environments. Potentially profound spillover effects on, for example, pollinator communities, may therefore be overlooked. 2. In this study, we compared plant communities, pollinator communities and plant–pollinator networks around beaver wetlands and human-created ponds. Specifically, we tested if these wetland types differ in terms of (1) plant species richness and community composition, (2) pollinator species richness and abundance, and the floral characteristics (number of species in flower and maximum flower coverage) to which pollinators respond and (3) specialisation of their plant-pollinator networks. 3. Plant composition but not species richness differed between the two wetland types. Beaver wetlands supported more ruderal and competitor indicator species, whereas human-created ponds had more stress tolerators. 4. Hoverfly richness (+29%), hoverfly abundance (+119%) and butterfly abundance (+45%) were higher in beaver wetlands, the former two being positively associated with number of species in flower and maximum flower coverage, and the latter with open habitats. Butterfly richness and both the richness and abundance of bees and moths showed no difference between wetland types. 5. Hoverflies were the dominant flower visitor in beaver wetlands and bees in human-created ponds, but network level specialisation did not differ significantly between the two wetland types. 6. Synthesis and applications. Our results show that beaver wetlands boost hoverfly richness/abundance and butterfly abundance and diversify foraging resources for pollinators while comparing favourably with human-created ponds for other pollinators. Support for beaver wetlands, in tandem with riparian buffers and pond margins, should therefore be advocated in agri-environment schemes to recognise the pollinator services they provide.