Phanerozoic predation intensity and diversity

Article By:

Huntley, John Warren Department of Geological Sciences, University of Missouri, Columbia, Missouri.

Last reviewed:2009

The idea that species interactions, such as predation, parasitism, or competition, helped shape the history of biodiversity is not a new one. Indeed, Charles Darwin compared the biotic world to a surface of tightly packed wedges, and the only way for a new species—in his metaphor, a wedge—to gain a foothold was to drive out another wedge. By observing species interactions in the modern living world, it seems apparent that organisms' struggles for food, habitat, and reproduction were the fundamental processes responsible for the biodiversity that we see today. Predation, the killing and consumption of an organism (prey) by another organism (predator), has been shown to be particularly important in determining species diversity in modern environments. The classic experiments of ecologist Robert Paine in intertidal environments in the Pacific Northwest illustrated the role of predators in increasing the number of species in a local environment. Paine removed the top invertebrate predator, the sea star Pisaster, from a shoreline environment, and the number of species in the experimental plot dropped from 15 to 8. The explanation is that by feeding—also termed “cropping”—predators prevent other species from monopolizing the environment and outcompeting their competitors. Steven M. Stanley extended the cropping hypothesis to explain the Cambrian explosion, a geologically sudden macroevolutionary event during which nearly all animal phyla appeared in the fossil record.

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