Geographic Variation and Phenotypic Plasticity of Body Size and Cell Size in the Lizard, Anolis Carolinensis

Patterns of geographic variation in body size and cell size have long fascinated biologists, and climatic variables have often been considered to explain such patterns. Environmental temperature can profoundly influence the phenotype, including body size. of ectotherms, and reptiles in particular. This dissertation presents four studies that examine how temperature shapes morphology on developmental and evolutionary timescales in the green anole lizard, Anolis carolinensis. The first three studies examined variation in and phenotypic plasticity of cell size and body size through laboratory experiments using eggs and juveniles from wild-caught females in five populations of A. carolinensis. The fourth study examined geographic variation in body size and cell size in 19 wild populations across the species range. Temperature-induced plasticity in cell size but not initial hatching size was demonstrated. However, subsequent differences in growth rates among juveniles reared in a common laboratory environment indicated a latent effect of incubation temperature on body size. Sampling of body size and red blood cell size from four eastern populations in the range suggested a latitudinal trend in body size and cell size. Rearing of offspring in a common environment indicated differences among populations in juvenile and, potentially, embryonic growth rates contributing to divergence in adult body size. Extended sampling of body size and cell size from 19 populations throughout the range, however, showed that inclusion of Florida populations heavily skewed geographic patterns because of the smaller body and cell size of anoles in the peninsular state. Exclusion of these populations revealed a negative relationship between latitude and both body size and muscle cell size, and no geographic trends in red blood cell size.