Local Habitat Features, but Not Isolation, Shape Alpine Odonate Assemblages: Implications for Modelling and Conservation

Abstract

Aim: Human impacts and climate change are intensifying the fragmentation of freshwater habitats, raising concerns about the ability of aquatic species to disperse between increasingly isolated habitat patches. To explore these dynamics, we used dragonflies and damselflies (Odonata) as a model taxon to examine how two principles of island biogeography—habitat isolation and quality—shape the community assembly of freshwater insects in a topographically diverse mountainous landscape. Location: Central southern Alps, Italy. Methods: We make use of openly available geodata to quantify the isolation of 99 sites in an Alpine region with well-sampled dragon and damselfly communities. We tested how isolation influences diversity, community composition, and the occurrences of individual species. Results: Isolation did not affect species richness, community composition, and the occurrence of most species. Instead, site elevation, habitat composition, and area played a more important role in shaping dragon- and damselfly communities. Main Conclusions: Odonata can freely disperse within a heterogeneous alpine landscape at a regional scale, calling into question proposals of creating artificial habitats to increase connectivity. Instead, habitat composition and site area had a stronger effect than isolation on all investigated aspects. Thus, conservation efforts should prioritise the protection of existing natural habitats and corridors. Additionally, our findings provide empirical support for the assumption of no dispersal limitation at a regional scale, common in many ecological null models of community assembly.