Sex-biased juvenile dispersal is adaptive but does not create genetic structure in island lizards

Dispersal is a potentially risky behavior that has several important implications for demography. Dispersal may be measured directly through behavioral observations or indirectly using genetic analyses. The direct approach is accurate but labor-intensive, whereas the indirect approach depends on population subdivision to infer dispersal events. Here, we combine field studies of behavior and natural selection in an island lizard (Anolis sagrei) to provide direct estimates of sex-specific dispersal and then compare these estimates to measures of population subdivision at both nuclear (biparental inheritance) and mitochondrial (uniparental inheritance) genetic markers. Juvenile males dispersed 4 times further than juvenile females. Natural selection acted against long-distance dispersal in females, but we measured no such selection on dispersal distance in males. Despite strong evidence for sex-biased dispersal accompanied by selection, we detected no population genetic signature of dispersal at either nuclear or mitochondrial loci. In closed populations, such as those occurring on small islands, repeated dispersal events may have important demographic consequences and yet produce no population genetic signature owing to continuous admixture of genotypes.