Meeting Abstract
Sex differences in selection result in intralocus sexual conflict when the same alleles have opposite effects on fitness in males and females, and the resulting genomic tug-of-war can constrain the independent evolution of the sexes. Although the evolution of sexual dimorphism suggests that these constraints can be overcome, field studies provide multiple examples of sexually antagonistic selection persisting on highly dimorphic traits.Sexual dimorphism often develops gradually over ontogeny, yet studies of sexually antagonistic selection in the wild have rarely spanned multiple life stages, so it remains unclear whether and how sexual antagonism differs with life stage. To address this, we estimated sex-specific selection gradients for multiple sexually dimorphic traits across juvenile and adult stages in a closed island population of brown anole lizards (Anolis sagrei). We used exhaustive sampling via mark-recapture over a two-year period to track the survival of more than 5,000 lizards spanning three generations. Sex differences in survival rates were apparent at both juvenile and adult life stages, creating higher opportunity for selection in males. Selection for large body size was strong in juveniles of both sexes, and antagonistic selection was absent prior to the development of dimorphism. After the development of sexual dimorphism in adults, we found sexually antagonistic selection on body size and on the size of a sexually dimorphic ornament, the dewlap. Selection on body size reinforced sexual dimorphism by favoring large males and small females, whereas selection on the dewlap was opposite the direction of dimorphism, favoring smaller dewlaps in males. This latter result suggests a cost associated with an elaborate, sexually selected ornament.
