Sex-specific consequences of juvenile dispersal for survival and reproduction in an island lizard

Dispersal is a costly, though potentially rewarding, behavior with important fitness consequences for juveniles. When the costs or benefits of juvenile dispersal differ between sexes, sex-biased dispersal should be favored, though such sex-specific consequences are rarely measured for multiple components of lifetime fitness in the wild. Here, we use detailed mark–recapture data from 4 annual cohorts of juveniles with associated estimates of juvenile survival and adult reproductive success from genetic parentage to measure natural selection on 2 dispersal phenotypes (binary dispersal propensity and continuous dispersal distance) in an island population of lizards (Anolis sagrei). Juvenile dispersal was consistently male-biased, with males exhibiting a higher propensity to disperse and dispersing twice as far as females. Males that dispersed had higher survival to adulthood and total fitness than males that remained philopatric, whereas fitness components did not differ between dispersing and philopatric females. Although this result indicates that the fitness benefits of dispersal are sex-specific, we found no difference in fitness components between dispersing and philopatric males after accounting for body size, which was positively correlated with dispersal. Likewise, we did not consistently detect direct selection on dispersal distance in either sex when including body size in multivariate selection analyses, nor did we find consistent correlational selection on combinations of body size and dispersal distance in either sex. We conclude that selection on juvenile dispersal propensity is sex-specific, but likely indirect and mediated through its positive association with body size in males.