Differences in thermal physiology shape the global distribution and diversity of vertebrates. Recent research reveals systematic shifts in the relative diversity of large predatory endotherms and ectotherms at sea with latitude and water temperature. These patterns have been theoretically linked to metabolic controls on predation. Elevated locomotory rates associated with endothermy are expected to enhance foraging success generally, but effects are predicted to be strongest in open, exposed habitats where speed and stamina are at a premium.
Here we extend we consider patterns of predator relative diversity and abundance from open, oceanic habitats to more physically complex coastal environments. We synthesize distributions from 998 species of endothermic birds and mammals, ectothermic sharks and bony fish, and mesothermic tuna, billfish and sharks to assess patterns of relative richness across environmental gradients. Findings are integrated into a recent energetic theory of foraging and competition.
Results/Conclusions
We observe systematic shifts in the thermoregulation and relative diversity of predators moving from coastal to pelagic habitats. The relative diversity of endotherms increases an order of magnitude in open water systems, paralleled by an increase in the relative frequency of mesothermic sharks and bony fish. In open habitats, such as the clear, well-lit waters of epipelagic systems, high metabolic power is most advantageous, with consequences for regional and global diversity. Our results shed light on the ecological drivers of endothermy and elevated metabolism.