Prof Mark Costello1
1Nord University
We connect evidence that 20oC is the most stable temperature for cellular processes with macroecology. Temperatures warmer than 20oC result in decreases in aquatic species’ tolerance to low oxygen; marine pelagic and benthic algal productivity; pelagic and benthic predation rates; and global species richness in pelagic fishes, plankton and benthic invertebrates. The thermal niche breadth of reef fishes and invertebrates is narrowest around 20oC, as also seen in microbes. A mathematical model that predicts thermal breadth should be minimized and species richness maximised at 20oC across all Domains of life, explains the decline in diverse biological responses above 20oC. Our literature search of species responses to temperature found that species richness maximises at ~20oC across life in air and water, including animals, plants and microbes. That life seems centred around ~20oC implies fundamental constraints, including biochemical ones, that compromise the ability of extant tropical species to adapt to higher temperatures.
