The effects of predation risk on mating system expression in a freshwater snail

Environmental effects on mating system expression are central to understanding mating system evolution in nature. Here I report the results from a quantitative-genetic experiment aimed at understanding the role of predation risk in the expression and evolution of life-history and mating-system traits in a hermaphroditic freshwater snail (Physa acuta). I reared 30 full-sib families in four environments that factorially contrast predation risk and mate availability and measured age/size at first reproduction, growth rate, a morphological defense, and the early survival of outcrossed/selfed eggs that were laid under predator/no-predator conditions. I evaluated the genetic basis of trade-offs among traits and the stability of the G matrix across environments. Mating reduced growth while predation risk increased growth, but the effects of mating were weaker for predator-induced snails and the effects of predation risk were weaker for snails without mates. Predation risk reduced the amou...