Ontogeny and Consistent Individual Differences Mediate Trophic Interactions.

Ecologists use species traits to predict responses to environmental change and, ultimately, to understand the composition of biological communities. However, this ignores known and substantial intraspecific variation that can have important consequences for species interactions and community composition. This within-species variation results from two distinct sources: ontogeny and consistent individual differences. Ontogeny and consistent differences interact to produce phenotypes, but the community-level consequences of this interaction have not been studied. Using larval dragonfly communities, I investigate patterns of intraguild predation by manipulating (1) consistent individual differences in activity rate and (2) the ontogeny of the focal and interacting species. I show that activity rate is a consistent individual trait but that the effect of activity rate on intraguild predation depends on the functional role of an organism in the community (predator or prey). An organism's functional role itself varies across ontogeny of both the focal and interacting individuals. I suggest that ontogeny and consistent individual differences interact to produce intraspecific variation, with consequences for species interactions, communities, and eco-evolutionary dynamics.