Effects of predation on life-history evolution in Utah chub (Gila atraria)

We compared eight populations of Utah chub (Gila atraria), isolated since t he late Pleistocene, to evaluate the relationship between predation by cutt hroat trout (Oncorhynchus clarki) and chub life histories. Utah chub popula tions that have historically coexisted with cutthroat trout show higher juv enile growth rates, delayed age at maturity, larger size at maturity, and l ower female reproductive effort than isolated populations with no predators . These results are consistent with life-history models of size-selective p redation, in which juvenile mortality is high relative to adult mortality. We evaluated temperature differences, resource availability, and phylogenet ic history as alternatives to the predation hypothesis. We conclude that li fe-history divergence among Utah chub populations is best explained by diff erences in predator-mediated mortality. This study is the first to evaluate effects of predation on life-history evolution in a long-lived prey specie s.