Glacier retreat erodes plant–insect interaction diversity

Abstract

Abstract The retreat of glaciers worldwide is causing changes in species diversity, community composition and species interactions. However, the impact of glacier retreat on interaction diversity and ecological networks remains poorly understood. An integrative understanding of network dynamics is of major importance to supporting biodiversity and ecosystem functioning after glacier extinction. Here, we address how glacier retreat affects the frequency, complexity, and diversity of plant–insect interactions, both directly and indirectly through biodiversity change. We surveyed flower visitors and analyzed visitation networks along the foreland of the Mont Miné glacier (Valais, Switzerland). As glacier retreat impacts both plant and insect communities, we observe sharp changes in the diversity of plant–insect interactions and the structure of pollination networks. We find an increase in the frequency of interactions following glacier retreat, but an ultimate decrease with glacier extinction. After controlling for the effects of floral diversity, interaction frequency showed a regular ‘universal’ pattern. Accordingly, the complexity of pollination networks and interaction diversity tends to change at constant rates with glacier retreat. Our results indicate that glacier retreat decreases biodiversity and influences the stability of ecological networks. The good news is that increasing floral diversity counteracts these impacts by increasing interaction diversity and supporting complexity. Slowing down woody encroachment and enhancing floral diversity may therefore be key strategies for halting the erosion of ecological networks while increasing biodiversity and ecosystem functioning.