Linking learning adaptation to trophic interactions: A brain size-based approach

Abstract

Given that food web structure potentially affects species coexistence and ecosystem functioning, exploration of the patterns and determinants of the resource-consumer interactions, the building blocks of food webs, should be of particular importance for successful maintenance of biodiversity and ecosystem services. 2. Ecological theory has demonstrated that rapid 'adaptation' via learning potentially alters the strength of trophic interaction, and thus, population dynamics. Increasing evidence suggests that learning improves foraging and anti-predator defence behaviours in diverse animal taxa and that cognitive ability is related to population establishment or persistence. However, only a few empirical studies have evaluated the community-level consequences of learning, probably owing to the difficulty in detecting learning-mediated changes at levels higher than the individual and in evaluating the learning ability of individual species. 3. Comparative studies, mostly conducted to identify selection pressures in brain evolution, suggest that brain size is an aggregate proxy for an organism's learning ability. Therefore, I propose a framework to analyse resource-consumer relationships based on information about the brain size of individual species, which will allow investigation into the effects of learning on food webs. 4. Evidence shows that brain size is related to trophic interactions. Earlier comparative analyses have revealed that diet is correlated with brain size in primates, mammals and insects. My analysis of 623 prey-predator pairs comprising 277 fish species indicates that a larger-brained predator tends to prey on a larger-brained prey; that relative brain size of prey is, on average, larger than that of the predator; and that our understanding of prey-predator pairs is improved by information about brain size. 5. A number of questions remain unanswered. Studies on how brain size is related to trophic interactions are limited to a few animal taxa. The factors leading to brain-related patterns in trophic interactions remain to be addressed. Brain-related patterns with respect to higher level biological organizations, such as whole food webs or chains, and inter-community comparison remain unexplored. Further studies are needed to confirm the general applicability of the hypotheses that relate brain size to trophic interactions and to evaluate the role of learning in shaping biological communities. © 2010 British Ecological Society.