Higher predation risk for insect prey at low latitudes and elevations.
Roslin T., Hardwick B., Novotny V., Petry WK., Andrew NR., Asmus A., Barrio IC., Basset Y., Boesing AL., Bonebrake TC., Cameron EK., Dáttilo W., Donoso DA., Drozd P., Gray CL., Hik DS., Hill SJ., Hopkins T., Huang S., Koane B., Laird-Hopkins B., Laukkanen L., Lewis OT., Milne S., Mwesige I., Nakamura A., Nell CS., Nichols E., Prokurat A., Sam K., Schmidt NM., Slade A., Slade V., Suchanková A., Teder T., van Nouhuys S., Vandvik V., Weissflog A., Zhukovich V., Slade EM.
Biotic interactions underlie ecosystem structure and function, but predicting interaction outcomes is difficult. We tested the hypothesis that biotic interaction strength increases toward the equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660-kilometer latitudinal gradient spanning six continents, we found increasing predation toward the equator, with a parallel pattern of increasing predation toward 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 consistent drivers of biotic interaction strength, a finding that needs to be integrated into general theories of herbivory, community organization, and life-history evolution.