Microgeographic Adaptation of Wood Frog Tadpoles to an Apex Predator

Rapid adaptation of defenses can alter ecological dynamics following introduction of a new predator. We tested for local adaptation in Wood Frog (Rana sylvatica) populations that face varying selection from an apex predator, the Marbled Salamander (Ambystoma opacum), which is expanding its distribution in the study region. We performed a reciprocal transplant experiment with Wood Frog eggs and tadpoles and tested survival of tadpoles when exposed to Marbled Salamander larvae in experimental predation trials. We also evaluated life history, behavioral, and morphological trait variation with respect to origin and transplant environments. We found that tadpoles from populations exposed to high risk from Marbled Salamanders survived better when raised in high-risk environments than tadpoles from low-risk populations. However, tadpoles from high-risk environments experienced lower survival than those from low-risk environments when raised in low-risk environments. Development rate, activity, and morphology differed among populations and environments. Faster development of high-risk populations in high-risk environments and activity patterns best explained observed survival differences. These results suggest that tadpoles have evolved adaptive plasticity at microgeographic scales in response to a mosaic of varying predation risk. Fine-scaled evolution of prey survival and local gene flow could enhance the resilience of Wood Frogs to this predator expansion. As warming winters allow Marbled Salamanders to increase in abundance and distribution, the rapid and fine-scaled evolution of their prey could mediate predicted changes to temporary pond communities and ecosystems. Rapid prey evolution might often promote ecological resilience to predator introductions.