GEOGRAPHIC-VARIATION IN LIZARD PHENOTYPES - IMPORTANCE OF THE INCUBATION ENVIRONMENT

Geographic variation in phenotypes can result from proximate environme ntal effects as well as from underlying genetic factors. Reciprocal tr ansplant experiments, in which organisms are moved from one area to an other, offer a powerful technique to partition the effects of these tw o factors. However, many studies that have utilized this technique hav e focused on the post-hatching organism only and ignored potential eff ects of environmental influences acting during embryonic development. We examined the phenotypic responses of hatchling scincid lizards (Lam propholis guichenoti) incubated in the laboratory under thermal regime s characteristic of natural nests in two study areas in southeastern A ustralia. Although the sites were less than 120 km apart, lizards from these two areas differed in thermal regimes of natural nests, and in hatchling phenotypes (morphology, locomotor performance). We incubated eggs from each area under the thermal regimes typical of both sites. Some of the traits we measured (e.g. hatchling mass and snout-vent len gth) shelved little or no phenotypic plasticity in response to differe nces in incubation conditions, whereas other traits (e.g. incubation p eriod, tail length, inter-limb length, body shape, locomotor performan ce) were strongly influenced by the thermal regime experienced by the embryo. Thus, a significant proportion of the geographic variation in morphology and locomotor performance of hatchling lizards may be direc tly induced by differences in nest temperatures rather than by genetic divergence. We suggest that future studies using the reciprocal trans plant design should consider environmental influences on all stages of the life-history, including embryonic development as well as post-hat ching life. (C) 1998 The Linnean Society of London.