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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.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Dr Nic Rawlence, Director Otago Palaeogenetics Lab and Senior Lecturer in Ancient DNA, Department of Zoology, University of Otago
The past is the key to the present. How biodiversity responded to climate change in the past can help scientists to predict how plants and animals may respond to human-driven climate change in the future.
Tim Womack and colleagues at Victoria University of Wellington and the British Museum of Natural History have used Aotearoa New Zealand’s shallow marine mollusc (i.e. seashells) fossil record to examine aspects of this big picture question. This study is only possible with an excellent fossil record, excellent collections and a diverse and well understood fauna – all of which New Zealand has.
Using the mollusc fossil record, Tim Womack and colleagues showed that over tens of millions of years, increasing ocean temperature due to natural climate change led to increased species richness (i.e. new species arising or species expanding their range) and functional redundancy (i.e. multiple species filling the same role in the ecosystem).
“While this may seem like good news regarding the potential impacts of human-driven climate change, increased species richness may come at the cost of the complete biological turnover of shallow marine molluscs, as has happened at the start of the last Ice Age 2.5 million years ago, and increasing numbers of invasive species, both of which would be very bad indeed.
