Extensive regional variation in the phenology of insects and their response to temperature across North America
Authors: Dunn Peter O. , Ahmed Insiyaa , Armstrong Elise , Barlow Natasha , Barnard Malcolm A. , Bélisle Marc , Benson Thomas J. , Berzins Lisha L. , Boynton Chloe K. , Brown T. Anders , Cady Melissa , Cameron Kyle , Chen Xuan , Clark Robert G. , Clotfelter Ethan D. , Cromwell Kara , Dawson Russell D. , Denton Elsie , Forbes Andrew , Fowler Kendrick , Fraser Kevin C. , Gandhi Kamal J. K. , Garant Dany , Hiebert Megan , Houchen Claire , Houtz Jennifer , Imlay Tara L. , Inouye Brian D. , Inouye David W. , Jackson Michelle , Jacobson Andrew P. , Jayd Kristin , Juteau Christy , Kautz Andrea , Killian Caroline , Kinnear Elliot , Komatsu Kimberly J. , Larsen Kirk , Laughlin Andrew , Levesque‐Beaudin Valerie , Leys Ryan , Long Elizabeth , Lougheed Stephen C. , Mackenzie Stuart , Marangelo Jen , Miller Colleen , Molano‐Flores Brenda , Morrissey Christy A. , Nicholls Emony , Orlofske Jessica M. , Pearse Ian S. , Pelletier Fanie , Pitt Amber L. , Poston Joseph P. , Racke Danielle M. , Randall Jeannine A. , Richardson Matthew L. , Rooney Olivia , Ruegg A. Rose , Rush Scott , Ryan Sadie J. , Sadowski Mitchell , Schoepf Ivana , Schulz Lindsay , Shea Brenna , Sheehan Thomas N. , Siefferman Lynn , Sikes Derek , Stanback Mark , Styrsky John D. , Taff Conor C. , Uehling Jennifer J. , Uvino Kathleen , Wassmer Thomas , Weglarz Kathryn , Weinberger Megan , Wenzel John , Whittingham Linda A. 
Published: March 2023

Climate change models often assume similar responses to temperatures across the range of a species, but local adaptation or phenotypic plasticity can lead plants and animals to respond differently to temperature in different parts of their range. To date, there have been few tests of this assumption at the scale of continents, so it is unclear if this is a large‐scale problem. Here, we examined the assumption that insect taxa show similar responses to temperature at 96 sites in grassy habitats across North America. We sampled insects with Malaise traps during 2019–2021 (N = 1041 samples) and examined the biomass of insects in relation to temperature and time of season. Our samples mostly contained Diptera (33%), Lepidoptera (19%), Hymenoptera (18%), and Coleoptera (10%). We found strong regional differences in the phenology of insects and their response to temperature, even within the same taxonomic group, habitat type, and time of season. For example, the biomass of nematoceran flies increased across the season in the central part of the continent, but it only showed a small increase in the Northeast and a seasonal decline in the Southeast and West. At a smaller scale, insect biomass at different traps operating on the same days was correlated up to ~75 km apart. Large‐scale geographic and phenological variation in insect biomass and abundance has not been studied well, and it is a major source of controversy in previous analyses of insect declines that have aggregated studies from different locations and time periods. Our study illustrates that large‐scale predictions about changes in insect populations, and their causes, will need to incorporate regional and taxonomic differences in the response to temperature.