Ecological community dynamics: 20 years of moth sampling reveals the importance of generalists for community stability

Species diversity is presently declining and homogenizing globally due to human land use changes and climate change effects. However, the causes of these declines are difficult to determine due to complex ecological interactions. Lepidopterans are a diverse and ecologically important group of insects that are declining in Britain and other parts of Europe. Long-term monitoring data made available in 2003 showed that 66% of observed species declined over the course of 35 years, however, it is not known what effect species losses has on ecosystem stability. Here, we assess long-term moth diversity dynamics in relation to climatic shifts over 20 years, and investigate the importance of stability in maintaining and conserving ecological communities. From 1993 to 2014, moth species data and abundances were recorded over 7,390 trapping nights. Overall, 376 species were recorded over 20-years, identifying seasonal and annual trends in species richness strongly associated with oscillations in temperature. Long-term stability, measured using mean-rank shifts and temporal variability, was indicative of significant positive associations between species diversity and temperature. Using rank shift analyses we were able to not only assess community stability dynamics, but also the individual species dynamics and their contribution to community diversity over time. We also noted generalist feeders were more associated with maintaining diverse species communities subjected to oscillating climatic conditions compared to specialist taxa. Overall, our study shows the benefit of utilizing community-based stability assessments to distill population level information from complex datasets, highlighting the need for long-term monitoring at the community level to explore impacts of environmental change on ecosystem function. (C) 2020 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.