Local prey community composition and genetic distance predict venom divergence among populations of the northern Pacific rattlesnake (Crotalus oreganus)

Identifying the environmental correlates of divergence in functional traits between populations can provide insights into the evolutionary mechanisms that generate local adaptation. Here, we assess patterns of population differentiation in expressed venom proteins in Northern Pacific rattlesnakes (Crotalus oreganus) from 13 locations across California. We evaluate the relative importance of major biotic (prey species community composition), abiotic (temperature, precipitation, and elevation) and genetic factors (genetic distance based on RADseq loci) as correlates of population divergence in venom phenotypes. We found that over half of the variation in venom composition is associated with among-population differentiation for genetic and environmental variables, and that this variation occurred along axes defining previously observed functional trade-offs between venom proteins that have neurotoxic, myotoxic and hemorrhagic effects. Surprisingly, genetic differentiation among populations...