How ocean temperature shapes marine biodiversity over geological time scales

During the Cenozoic era, warmer oceans harbored more species with similar functional roles, according to a new study, which reveals how ocean temperature shapes biodiversity and biogeographic patterns over geological timescales. Studying how biodiversity patterns have changed in the past can be useful for understanding the long-term ecological impacts of current, human-induced climate warming. The spatial and temporal structuring of biodiversity can be measured in terms of species richness (overall number of species) and functional richness (the number of common functional traits shared between species) over time in a given area. While more is known about patterns related to species richness change over time, less is known about patterns related to functional richness. Recent marine ecological research indicates high levels of functional redundancy (duplication of functional roles by multiple species) in tropical-subtropical regions, suggesting that latitudinal gradients of climate or temperature may drive this measure. Understanding this relationship is important because modern ecological studies suggest that functional redundancy may bolster ecosystem resilience to future environmental change. Using the fossil record of shallow-marine mollusks from New Zealand spanning roughly 40 million years, Tom Womack and colleagues illustrate the positive relationship between species richness, functional redundancy, and ocean temperature over geological timescales. Womack et al. found that both richness and redundancy increased in periods with warmer waters, revealing a long-lived and persistent relationship between the spatial and functional structuring of biodiversity and temperature. “Taken at face value, our results suggest that oceanic temperature should increase net species richness and functional redundancy in New Zealand over long timespans, particularly as we shift to a climate more representative of pre-Pleistocene conditions,” write the authors.