Predation and Resource Availability Interact to Drive Life-History Evolution in an Adaptive Radiation of Livebearing Fish

Predation risk and resource availability are two primary factors predicted by theory to drive the evolution of life histories. Yet, disentangling their roles in life-history wild is challenging because (1) often co-vary across environments, (2) environmental effects on phenotypes can mask patterns genotypic evolution. Here, we use model system post-Pleistocene radiation Bahamas mosquitofish ( Gambusia hubbsi ) inhabiting blue holes provide a strong test predation resources evolution, as do not this attempted minimize raising eight populations under common laboratory conditions. We tested priori predictions predation- resource-driven five traits. found that largely reflected complex interactions availability. High has driven higher fecundity, smaller offspring size, more frequent reproduction, slower growth rate—but predation-driven divergence primarily occurred environments with relatively high availability, was generally greater within having risk. This implies selection histories overrides from predators when particularly scarce. While several results matched predictions, added nuance interdependence among selective agents, some did not. For instance, only levels, risk, explained evolutionary change male age at maturity, rapid sexual maturation higher-resource environments. also faster (not slower) juvenile rates low-resource low-predation probably caused these high-competition scenarios favoring efficiency. Our approach, using common-garden experiments natural low- high-predation span continuum provides powerful way deepen our understanding Overall, it appears adaptive resulted interplay between resources, underscoring need for increased attention sophisticated agents driving phenotypic diversification.