Biotic interactions underlie ecosystem structure and function, but predicting interaction outcomes is difficult. We tested the hypothesis that biotic interaction strength increases towards the Equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660 km latitudinal gradient spanning six continents, we found increasing predation towards the Equator – with a parallel pattern of increasing predation towards lower elevations. Patterns across both latitude and elevation were driven by arthropod predators, with no systematic trend in attack rates by birds or mammals. These matching gradients at global and regional scales suggest coherent drivers of biotic interaction strength, a finding which needs to be integrated into general theories of herbivory, community organization, and life history evolution.
The Global Dummy Caterpillar Project is:
Tomas Roslin (Project Leader), Eleanor Slade (Project Leader), Vojtech Novotny (Project Leader), Bess Hardwick (Project Coordinator)
Data contributors:
Ashley Asmus, Isabel C. Barrio, Yves Basset, Andrea Larissa Boesing, Timothy C. Bonebrake, Erin K. Cameron, Wesley Dáttilo, David A. Donoso, Pavel Drozd, Claudia L. Gray, David S. Hik, Sarah J. Hill, Tapani Hopkins, Shuyin Huang, Bonny Koane, Benita Laird-Hopkins, Liisa Laukkanen, Owen T. Lewis, Sol Milne, Isaiah Mwesige, Akihiro Nakamura, Colleen S. Nell, Elizabeth Nichols, William K. Petry, Alena Prokurat, Katerina Sam, Niels M. Schmidt, Alison Slade, Victor Slade, Alžběta Suchanková, Tiit Teder, Saskya van Nouhuys, Vigdis Vandvik, Anita Weissflog, & Vital Zhukovich