Body-size reduction in vertebrates following the end-Devonian mass extinction

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Science  13 Nov 2015:
Vol. 350, Issue 6262, pp. 812-815
DOI: 10.1126/science.aac7373

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The small will inherit the Earth…

Understanding how communities and ecosystems recovered from the previous five global extinction events sheds light on how extinctions shape broad patterns of biodiversity. Sallan et al. looked across vertebrate species during and after the Devonian extinction (see the Perspective by Wagner). Small-bodied species, with rapid reproductive rates, dominated post-extinction communities, despite the presence of many successful large-bodied species before the extinction. This pattern mimics, to some degree, current patterns of extinction, suggesting that we might expect similar loss of large-bodied species if we continue along our current path.

Science, this issue p. 812; see also p. 736


Following the end-Devonian mass extinction (359 million years ago), vertebrates experienced persistent reductions in body size for at least 36 million years. Global shrinkage was not related to oxygen or temperature, which suggests that ecological drivers played a key role in determining the length and direction of size trends. Small, fast-breeding ray-finned fishes, sharks, and tetrapods, most under 1 meter in length from snout to tail, radiated to dominate postextinction ecosystems and vertebrae biodiversity. The few large-bodied, slow-breeding survivors failed to diversify, facing extinction despite earlier evolutionary success. Thus, the recovery interval resembled modern ecological successions in terms of active selection on size and related life histories. Disruption of global vertebrate, and particularly fish, biotas may commonly lead to widespread, long-term reduction in body size, structuring future biodiversity.

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