A positive relationship between functional redundancy and temperature in Cenozoic marine ecosystems

Abstract

More species in warm waters Past patterns of diversity can be used as a baseline for understanding how current human-induced changes are affecting biodiversity. Womack et al. looked at mollusk fossils from 40 million years ago in New Zealand to determine how ocean temperatures influence species richness and functional redundancy, a measure of how many species fill similar ecological roles. Both richness and redundancy increased in periods with warmer water, meaning that there were more species and that those species often filled similar ecological roles. Such ecological redundancy can increase ecosystem resilience, and understanding its relationship with temperature can help us determine where human activities are driving change. Science, abf8732, this issue p. 1027 Ocean temperature has shaped the biodiversity of marine organisms over geological time scales. The long-term effects of climate change on biodiversity and biogeographic patterns are uncertain. There are known relationships between geographic area and both the number of species and the number of ecological functional groups—termed the species-area relationship and the functional diversity–area relationship, respectively. We show that there is a positive relationship between the number of species in an area, the number of ecological functional groups, and oceanic temperature in the shallow-marine fossil record of New Zealand over a time span of ~40 million years. One implication of this relationship is that functional redundancy increases with temperature. This reveals a long-lived and persistent association between the spatial structuring of biodiversity, the temperature-dependence of functional redundancy, and shallow-marine biodiversity in mid-latitudes.