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Local prey community composition and genetic distance predict venom divergence among populations of the northern Pacific rattlesnake ( Crotalus oreganus )
Author(s) -
Holding Matthew L.,
Margres Mark J.,
Rokyta Darin R.,
Gibbs H. Lisle
Publication year - 2018
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/jeb.13347
Subject(s) - biology , venom , abiotic component , predation , local adaptation , genetic variation , population , crotalus , genetic divergence , ecology , isolation by distance , adaptation (eye) , evolutionary biology , zoology , genetic diversity , genetic structure , genetics , gene , demography , neuroscience , sociology
Abstract 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 RAD‐seq 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 was the best predictor of venom divergence, accounting for 46% of overall variation, whereas differences in prey community composition and abiotic factors explained smaller amounts of variation (23% and 19%, respectively). The association between genetic differentiation and venom composition could be due to an isolation‐by‐distance effect or, more likely, an isolation‐by‐environment effect where selection against recent migrants is strong, producing a correlation between neutral genetic differentiation and venom differentiation. Our findings suggest that even coarse estimates of prey community composition can be useful in understanding the selection pressures acting on patterns of venom protein expression. Additionally, our results suggest that factors other than adaptation to spatial variation in prey need to be considered when explaining population divergence in venom.