Climate drivers of adult insect activity are conditioned by life history traits

Michael Belitz, Vijay Barve, Joshua Doby, Jessica Oswald, Neeka Sewnath, Mitchell Walters, Narayani Barve, Kamala Earl, Nicholas Gardner, Robert P. Guralnick and Brian Stucky, Florida Museum of Natural History, Gainesville, FL, Maggie Hantak, University of Florida, Elise Larsen, Biology, Georgetown University, Washington, DC, Daijiang Li, Louisiana State University, Baton Rouge, LA, Jessica Oswald, Biology, University of Nevada, Reno, NV

Background/Question/Methods
Shifts in the seasonal timing of biological events are one of the most apparent effects of climate change on biodiversity. While the climate variables and life history traits that determine when adult insects emerge are well documented, little is known about what factors determine when activity periods terminate. Likewise, the drivers of total duration of adult activity are not well documented along broad climate gradients. Understanding these phenological patterns across broad spatial and taxonomic scales is important due to the critical roles insects play in pollination, nutrient cycling, and trophic interactions. Additionally, insect phenological lability is a key determinant of which species can adapt and potentially thrive under environmental change. Here, we used openly available community-science and museum specimen records to investigate the effects of climate and urbanization on the timing of emergence, termination, and duration of adult insect activity. Phenology estimates were generated across North America for 101 species representing six orders, which vary in life history traits.
Results/Conclusions
We found strong evidence of region-specific climate and life history effects on insect phenology. For example, warm, wet areas had earlier emergence and longer durations than cooler, wet regions. We also found detritivores and species that spend their larval life stage in freshwater extend their activity period most rapidly in response to increases in regional temperature. Conversely, species that spend their larval life stage underground have relatively constant durations regardless of the regional temperature. Multivoltine and univoltine species extended their period of adult activity similarly in warmer conditions. Longer adult durations may represent a general response to warming, but also may highlight that our understanding of life history trait variation remains incomplete. Our study presents a framework to answer fundamental questions about adult insect phenology at a continental scale, and provides a basis for predicting how species will respond to environmental change.