Consumption rates and trophic interaction strengths are constrained by dimensionality of consumer search space

Background/Question/Methods

Consumers and resources interact in a wide array of habitats ranging from desert floors to pelagic zones in oceans and lakes. A mechanistic understanding of the effects of physical differences between such contrasting habitats on species interactions remains a major challenge in ecology. Habitat dimensionality may be one important factor determining trophic interaction strengths because consumers have opportunities to encounter resources more frequently in three-dimensions (3D) than two-dimensions (2D). We analyze taxonomically diverse data and develop theory to explore the importance of dimensionality

Results/Conclusions

Our data analysis reveals that across all major habitats and a wide range of taxa, interaction dimensionality - the space in which consumers search for resources – strongly impacts per-capita consumption rate and thus trophic interaction strength in. In 2D interactions, common in terrestrial and benthic habitats, consumption rates scale sub-linearly with consumer body mass. In 3D interactions, common in pelagic habitats, scaling is super-linear. These results contradict current assumptions of a dimension-independent exponent (∼0.75). We derive mechanistic theory that explains these patterns. This theory also makes novel and empirically realistic predictions about dimension-dependent species coexistence and abundances. Our quantitative framework yields realistic predictions of trophic interaction strengths across diverse habitats and taxa, and holds major implications for understanding both, the evolution of consumer-resource interactions, and the dynamics of populations and food-webs.