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Ecologically diverse clades dominate the oceans via extinction resistance

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Science  28 Feb 2020:
Vol. 367, Issue 6481, pp. 1035-1038
DOI: 10.1126/science.aax6398

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Resisting extinction

Prevailing evolutionary wisdom tells us that ecological differentiation leads to speciation. Whether this pattern can be seen over paleontological time, however, has been difficult to test. Knope et al. looked at a dataset of thousands of modern and extinct marine groups and found the relationship to be more complex than expected. Ecological diversification is associated with lower rates of origination, and the taxonomical richness seemingly associated with these groups is due to resistance to extinction. Furthermore, the researchers found that the strong association between ecological differentiation and taxonomic diversity is a recent development shaped by extinction events over time.

Science, this issue p. 1035

Abstract

Ecological differentiation is correlated with taxonomic diversity in many clades, and ecological divergence is often assumed to be a cause and/or consequence of high speciation rate. However, an analysis of 30,074 genera of living marine animals and 19,992 genera of fossil marine animals indicates that greater ecological differentiation in the modern oceans is actually associated with lower rates of origination over evolutionary time. Ecologically differentiated clades became taxonomically diverse over time because they were better buffered against extinction, particularly during mass extinctions, which primarily affected genus-rich, ecologically homogeneous clades. The relationship between ecological differentiation and taxonomic richness was weak early in the evolution of animals but has strengthened over geological time as successive extinction events reshaped the marine fauna.

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