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The Rise and Fall of Fishes: How Macroecology and Global Events Shape Vertebrate Evolution

Biological evolution was originally understood as a gradual, internally-driven process, and standing biodiversity entirely the result of the slow accumulation of positive changes. It is now clear that macroevolution (above species level) proceeds in booms and busts. It is influenced by emergent multiscale processes, which can turn short-term positive traits into long-term negatives and alter rates of evolutionary change. Because these processes play out over thousands to millions of years, they cannot be observed on generational timescales. Fortunately, the fossil record preserves this evolutionary history, documenting the responses of lineages to myriad conditions global and local. Here. I show the potential of this database of natural experiments, using examples in which I applied novel approaches from disparate fields to the vertebrate fossil record of the Devonian-Mississippian (419- 323 million years ago). This critical interval in vertebrate evolution contained both repeated rounds of diversification under varied conditions and a major climate- driven mass extinction event. These investigations have already revealed new and surprising information on the rise of modern fishes and faunas, the evolutionary outcomes of gradual and sudden climate change, the drivers of adaptive radiation, the origins of “living fossils,” and the role of macroecology in shaping evolution. Many of these results have overturned previous hypotheses, opening new paths of inquiry. Devonian-Carboniferous patterns and processes were likely repeated under similar conditions throughout evolutionary history, and might represent generalities in biological macroevolution.