Biogeography of bird and mammal trophic structures

Does climate determine the trophic organization of communities around the world? A recent study showed that a limited number of community trophic structures emerge when co-occurrence of trophic guilds among large mammals is examined globally. We ask whether the pattern is general across all terrestrial mammals (n = 5272) and birds (n = 9993). We found that the six community-trophic structures previously identified with large mammals are largely maintained when all mammals and birds are examined, both together and separately, and that bioclimatic variables, including net primary productivity (NPP), are strongly related to variation in the geographical boundaries of community trophic structures. We argue that results are consistent with the view that trophic communities are self-organized structures optimizing energy flows, and that climate likely acts as the main control parameter by modulating the amount of solar energy available for conversion by plants and percolated through food webs across trophic communities. Gradual changes in climate parameters would thus be expected to trigger abrupt changes in energy flows resulting from phase transitions (tipping points) between different dynamical stable states. We expect future research to examine if our results are general across organisms, ecosystems, scales and methodologies, and whether inferences rooted in complex systems theory are supported. The emergence of general patterns in the functional properties of animal communities at broad scales supports the emergence of food-web biogeography as a sub-discipline of biogeography focused on the analysis of the geographical distributions of trophic relationships among organisms.