"A metabolic constraint on the biogeography of marine animals: Implications for species richness and climate-driven extinction"
Oxygen played a key role in the evolution of marine ecosystems. However, it has not generally been considered a major constraint on the contemporary biogeography of species outside regions of exceptionally low O2. I will present a combination of physiological, climate, and species distribution data, to argue that the equatorward range limits of diverse aerobic species are governed by the ratio of oxygen supply and demand, even in well-oxygenated regions. These limits correspond to an energetic requirement for organismal activity of about 2-5 times that at rest, a ratio that is shared by most terrestrial species and thus appears fundamental. This metabolic constraint predicts patterns of species richness that are consistent with modern species distributions. It also implies a rapid loss of viable habitat due to the combination of warming and deoxygenation that accompany climate warming. Earth System Model simulations of climate warming at the Permian-Triassic boundary predict local extinction rates and patterns similar to what is observed in the fossil record. These results provide a mechanistic and empirically-based means for evaluating the biodiversity loss that may attend anthropogenic climate warming. [Background reading]