Skeletal marine animal biodiversity is built by families with long macroevolutionary lag times

Abstract

The clade dynamics of marine animals have changed markedly over the Phanerozoic.Long-term diversification is associated with decreasing origination and extinction rates, and with increasing taxon longevity. Here, we use the diversification trajectories of skeletal non-colonial marine families to infer the mechanisms which generated these trends. Suggested mechanisms behind these trends include stochastic extinction of taxa with high evolutionary volatility, and selection for traits that buffer against extinction. We find an increasing predominance of Phanerozoic families with long lag times between first appearance and peak diversity, over those with 'early burst' diversification trajectories. Long-lag families persisted for longer, had lower evolutionary volatilities, higher genus-level occupancies, and genera with larger niche breadths than early-burst families. However, they do not preferentially show ecological modes known to protect against extinction. We interpret the rise of the long lag families to reflect an intensification of ecosystem-level mechanisms supporting both long-term coexistence and transient dynamics, which increased the capacity of marine ecosystems to accommodate highly diverse communities.

Evolvability and Macroevolution: Overview and Synthesis

“…extrinsic events-prior to phenotypic expansions (see Donoghue & Sanderson, 2015;Stroud & Losos, 2016;Jablonski, 2017a). Such contingencies are most clearly seen in macroevolutionary lags, the geologically long interval between the inception of a novelty or clade and its taxonomic or phenotypic diversification (Jablonski & Bottjer, 1990), which appear to be widespread or even the general rule (Jablonski, 2017a;Halliday et al, 2019;Kröger & Penny, 2020;Ramírez-Barahona et al, 2020;Simões et al, 2020, Erwin, Bottjer, 1990 andPatzkowsky, 1995 on bryozoans without citing them). Such lags can be valuable analytical tools, providing a novel framework for evaluating intrinsic and extrinsic factors, by pinpointing an apparent increase in evolvability at a specific point in a clade's history.…”

“…Here the macroevolutionary evidence is less clear, if the metric is the growth of disparity relative to diversity-- the time of maximum disparity is measured relative to the total duration of each clade, and not against its taxonomic diversity profile through time, and more than half of their included studies show maximum disparity near the middle of a clade's history. Integrating the early-disparity findings of Hughes et al (2013) with the macroevolutionary-lag findings of Kröger and Penny (2020), superficially contradictory but actually dealing in different currencies, should clarify matters. Testing for variation in early and late members of clades originating at different points in geologic time would also be valuable-as Webster (2019) observes, the few direct tests have involved trilobite lineages with early members embedded in the Cambrian Explosion, and thus may be addressing a different hypothesis.…”