Climate change and the variability in community structure of Alpine Lepidoptera: unstable spring and fuzzy autumn

Abstract

The current increase in annual temperatures is altering spatial distribution and timing of activity patterns, i.e. phenology, of many animal and plant species. Theory predicts consequences of altered phenology at the community level and possible mismatches within food chains. We inferred temporal changes in Lepidoptera phenology in a mountainous region of northern Austria under climate change and their implications for community structure and stability. Long-term records (1990‒2022) representing 110,794 records of 1838 Lepidoptera species at two altitudinal belts served to assess annual phenologies at a weekly resolution. We calculated the shifts in community structure from Sørensen and Spearman rank order similarities and quantified respective temporal trends in similarity across the study period from linear and polynomic models. The observed temporal trends towards earlier appearance in spring and prolonged activity in autumn caused significant trends towards community disassembly at lower altitudes throughout the vegetation period. These trends were most pronounced in summer and regard both, community composition and dominance hierarchy. At higher altitudes, trends towards community disassembly were less visible throughout the vegetation period. Community disassembly alters food web structures and affect species interactions, particularly pollination and possibly insect and plant diversity. Further studies need to assess the long-term effects of community disassembly on Alpine ecosystem functioning.