Meeting Abstract

37.5  Thursday, Jan. 5  Sexual dimorphisms in Anolis lizard behavior and morphology: the result of niche partitioning or sexual selection? JOHNSON, M.A.*; SANGER, T.J.; SPARKS, M.N.; LOSOS, J.B.; Trinity University, San Antonio, TX; Harvard University; Trinity University, San Antonio, TX; Harvard University

Sexual dimorphisms in size and shape may result from ecological differences between the sexes or from sexual selection. Here, we examined the behavior and morphology of males and females of the two species of Anolis lizards that occur on Cayman Brac, A. sagrei and A. maynardi, to determine differences in traits of ecological importance (habitat use, foraging behavior, and limb dimensions) and traits potentially under sexual selection (social display, dewlap size, and body size). We also measured head dimensions, which could be associated with foraging and sexual selection, as biting is important in both prey capture and male-male conflicts. In both species, the sexes differed in display behavior and habitat use, but not foraging behavior, suggesting that sexual dimorphisms may be influenced by both sexual selection and some aspects of ecological niche partitioning. We found significant size and shape dimorphisms for the two species, with both more pronounced in A. maynardi. Variation in head length is the predominant morphological difference between the species and sexes. To more directly assess the potential roles of morphological traits in sexual selection, we used controlled behavioral trials to distinguish whether particular traits may be more strongly associated with male competition or female choice. Although the A. sagrei behavioral trials were largely inconclusive, in the A. maynardi behavioral trials, we found that longer-bodied males with shorter snouts were more likely to be dominant over other males, while males with longer snouts appeared to be preferred by females. This suggests the intriguing possibility that in A. maynardi, differing traits influence the two modes of sexual selection.