Mass extinctions alter extinction and origination dynamics with respect to body size

Abstract

Whether mass extinctions and their associated recoveries represent an intensification of background extinction and origination dynamics versus a separate macroevolutionary regime remains a central debate in evolutionary biology. The previous focus has been on extinction, but origination dynamics may be equally or more important for long-term evolutionary outcomes. The evolution of animal body size is an ideal process to test for differences in macroevolutionary regimes, as body size is easily determined, comparable across distantly related taxa and scales with organismal traits. Here, we test for shifts in selectivity between background intervals and the ‘Big Five’ mass extinction events using capture–mark–recapture models. Our body-size data cover 10 203 fossil marine animal genera spanning 10 Linnaean classes with occurrences ranging from Early Ordovician to Late Pleistocene (485–1 Ma). Most classes exhibit differences in both origination and extinction selectivity between background intervals and mass extinctions, with the direction of selectivity varying among classes and overall exhibiting stronger selectivity during origination after mass extinction than extinction during the mass extinction. Thus, not only do mass extinction events shift the marine biosphere into a new macroevolutionary regime, the dynamics of recovery from mass extinction also appear to play an underappreciated role in shaping the biosphere in their aftermath.

The impact of the Pliensbachian–Toarcian crisis on belemnite assemblages and size distribution

“…The pattern of increase rather than decrease in median body size is reminiscent of similar patterns reported from various mass extinction events at coarser stratigraphic resolution (Payne et al, 2016). These observations might hint that both origination and extinction dynamics play a large role in driving body size distribution in assemblages (Monarrez et al, 2021) surrounding such events then commonly embraced (Rego et al, 2012)-even at more highly resolved spatial (regional) and temporal (Chronozone) scales.…”

“…We find support for a marked taxonomic turnover coinciding with an increase in median size within assemblages across the T-OAE in the five basins we could study in detail. This highlights the importance of extinction and origination dynamics in driving shifts in body size distribution (Monarrez et al, 2021).…”

How predictable are mass extinction events?

“…A key functional trait that could be included in future analyses is body size, which is relevant because it controls the rate at which an organism uses energy and resources. In addition, body size has previously been found to be a good predictor of extinction in the marine realm over the Phanerozoic [43,69,81]. Extinction selectivity based on body size has also been found to show different patterns between intervals with low extinction rates and mass extinctions: during intervals with low extinction rates, smaller species are preferentially lost, while during mass extinctions, typically larger species preferentially go extinct [69,82].…”

“…One explanation as to why extinction selectivity during mass extinctions is so difficult to predict is that mass extinctions and the diversification events that follow them are highly selective [44,61,69], fundamentally altering the taxonomic and functional composition of the oceans [70][71][72]. This created stark differences between pre-extinction faunas, shifting the ecological baseline on which each subsequent mass extinction acted (figure 2).…”

High lineage survivorship across the end-Devonian Mass Extinction suggested by a remarkable new Late Devonian actinopterygian

“…Body size represents an important correlate of many aspects of life history and ecology, with many questions centering on impacts of body size during intervals of biotic crisis. Across all marine groups, selectivity on body size is more conspicuous during mass extinctions and their recovery intervals 58 . Decreases of mean body size associated with the Devonian-Carboniferous boundary have previously been reported in many vertebrate clades, including actinopterygians 13 .…”