Morphospace expansion paces taxonomic diversification after end Cretaceous mass extinction


Highly resolved palaeontological records can address a key question about our current climate crisis: how long will it be before the biosphere rebounds from our actions? There are many ways to conceptualize the recovery of the biosphere; here, we focus on the global recovery of species diversity. Mass extinction may be expected to be followed by rapid speciation, but the fossil record contains many instances where speciation is delayed—a phenomenon about which we have a poor understanding. A probable explanation for this delay is that extinctions eliminate morphospace as they curtail diversity, and the delay in diversification is a result of the time needed for new innovations to rebuild morphospace, which can then be filled out by new species. Here, we test this morphospace reconstruction hypothesis using the morphological complexity of planktic foraminifer tests after the Cretaceous–Palaeogene mass extinction. We show that increases in complexity precede changes in diversity, indicating that plankton are colonizing new morphospace, then slowly filling it in. Preliminary diversification is associated with a rapid increase in the complexity of groups refilling relict Cretaceous ecospace. Subsequent jumps in complexity are driven by evolutionary innovations (development of spines and photosymbionts), which open new niche space. The recovery of diversity is paced by the construction of new morphospace, implying a fundamental speed limit on diversification after an extinction event.

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Fig. 1: Planktic foraminifer diversity and test compexity.
Fig. 2: Comparison of Early Palaeogene climate events with planktic foraminifer diversity and complexity trends.

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All data and code related to this study are available at


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The authors acknowledge support to C.M.L. via NSF-OCE-1737351. We are also grateful for the efforts of the scientific drilling community over the past 50 years in collecting the deep-sea cores that form the bulk of large datasets such as this.

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Both authors contributed to data interpretation, figure plotting, and writing and editing the manuscript. A.J.F. wrote the R code and performed the morphometric measurements.

Correspondence to Christopher M. Lowery.

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Lowery, C.M., Fraass, A.J. Morphospace expansion paces taxonomic diversification after end Cretaceous mass extinction. Nat Ecol Evol 3, 900–904 (2019).

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