The contributions of evolutionary divergence and phenotypic plasticity to geographic variation in the western fence lizard, Sceloporus occidentalis

Abstract

3 Local genetic adaptation and phenotypic plasticity are two mechanisms that can have marked effects on the morphology, performance, and behaviour of animals, producing geographic variation among populations. However, few studies have examined how these mechanisms interact during ontogeny to shape organismal phenotypes. We incubated eggs of the western fence lizard, Sceloporus occidentalis, from four populations (representing two latitudes and altitudes) in either a warm or cool environment in the laboratory. We then raised the hatchlings under common laboratory conditions, measured morphological and performance traits until 5 weeks of age, and compared juvenile morphology with that of field-caught adults from each population. The results obtained indicate that some phenotypic traits that contribute to performance (body size, hindlimb length, head shape) were relatively canalized in juveniles and differed among populations in a way that was consistent with adults from their population of origin. However, other traits (forelimb length, inter-limb length, mass, tail length), showed significant effects of incubation temperature, and this environmentally induced variation persisted throughout the experi- ment. Although selection pressure may be stronger for traits that are integral to survival, developmental effects might still have a lasting impact on traits less important to organismal fitness. We discuss the results obtained in the present study the context of the life history of these animals. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 84-98. ADDITIONAL KEYWORDS: development - incubation - local adaptation - morphology - ontogeny - performance - reaction norm - temperature.