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Increase in predator-prey size ratios throughout the Phanerozoic history of marine ecosystems

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Science  16 Jun 2017:
Vol. 356, Issue 6343, pp. 1178-1180
DOI: 10.1126/science.aam7468

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Bigger and badder

The escalation hypothesis posits that predator size has increased over time, leading to increased motility and defense in prey organisms. Although influential, the hypothesis has been difficult to test. Klompmaker et al. looked at predator drill holes in bivalve shells across 500 million years. Drill-hole size did increase, whereas prey size remained relatively constant. This changing predator-prey size ratio suggests that the number of prey consumed likely increased, a factor facilitated by greater complexity of food webs and availability of nutrient-dense prey.

Science, this issue p. 1178

Abstract

The escalation hypothesis posits that predation by increasingly powerful and metabolically active carnivores has been a major driver of metazoan evolution. We test a key tenet of this hypothesis by analyzing predatory drill holes in fossil marine shells, which provide a ~500-million-year record of individual predator-prey interactions. We show that drill-hole size is a robust predictor of body size among modern drilling predators and that drill-hole size (and thus inferred predator size and power) rose substantially from the Ordovician to the Quaternary period, whereas the size of drilled prey remained stable. Together, these trends indicate a directional increase in predator-prey size ratios. We hypothesize that increasing predator-prey size ratios reflect increases in prey abundance, prey nutrient content, and predation among predators.

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