Abstract
Ecosystems are being altered on a global scale by the extirpation of top predators. The ecological effects of predator removal have been investigated widely; however, predator removal can also change natural selection acting on prey, resulting in contemporary evolution. Here we tested the role of predator removal on the contemporary evolution of trophic traits in prey. We utilized a historical introduction experiment where Trinidadian guppies (Poecilia reticulata) were relocated from a site with predatory fishes to a site lacking predators. To assess the trophic consequences of predator release, we linked individual morphology (cranial, jaw, and body) to foraging performance. Our results show that predator release caused an increase in guppy density and a “sharpening” of guppy trophic traits, which enhanced food consumption rates. Predator release appears to have shifted natural selection away from predator escape ability and towards resource acquisition ability. Related diet and mesocosm studies suggest that this shift enhances the impact of guppies on lower trophic levels in a fashion nuanced by the omnivorous feeding ecology of the species. We conclude that extirpation of top predators may commonly select for enhanced feeding performance in prey, with important cascading consequences for communities and ecosystems.
Highlights
Top predator removal is reshaping communities and ecosystems at an alarming rate [1]
While much effort has gone into understanding the effects of fisheries harvest on trophic interactions in truncated food chains [9,10,11] and on the contemporary evolution of harvested populations themselves [12,13], almost nothing is known about the indirect effects of predator removal on prey evolution and its consequences for trophic interactions
Laboratory studies of ecoevolutionary dynamics have shown that, when prey species face an evolutionary trade-off between predator avoidance and competitive ability, release from predation can sharpen the resource use traits of prey, with implications for ecological interactions [21,22,55,56]
Summary
Top predator removal is reshaping communities and ecosystems at an alarming rate [1]. Nowhere are these changes more dramatic than in aquatic ecosystems, where predatory fishes are common targets of human harvest. Fisheries harvest has caused widespread and dramatic reductions in food chain length in both marine and freshwater ecosystems [2,3,4,5,6]. It has become widely recognized that fisheries harvest can cause direct evolutionary changes in harvested fish populations [12,13]. The harvest of top predators, and the ensuing release from predation pressure, may have important implications for prey evolution [14,15] – and by extension the community and ecosystem properties affected by altered prey traits
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