Effects of Predation on Life-History Evolution in Utah Chub (Gila atraria)

Abstract

We compared eight populations of Utah chub (Gila atraria), isolated since the late Pleistocene, to evaluate the relationship between predation by cutthroat trout (Oncorhynchus clarki) and chub life histories. Utah chub populations that have historically coexisted with cutthroat trout show higher juvenile growth rates, delayed age at maturity, larger size at maturity, and lower female reproductive effort than isolated populations with no predators. These results are consistent with life-history models of size-selective predation, in which juvenile mortality is high relative to adult mortality. We evaluated temperature differences, resource availability, and phylogenetic history as alternatives to the predation hypothesis. We conclude that lifehistory divergence among Utah chub populations is best explained by differences in predator-mediated mortality. This study is the first to evaluate effects of predation on life-history evolution in a long-lived prey species.