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 four annual cohorts of juveniles with associated
estimates of juvenile survival and adult reproductive success from genetic
parentage to measure natural selection on two 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.