Sex-specific dispersal responses to inbreeding and kinship

Dispersal is a fundamental life history trait in animals that governs species distribution and population dynamics. However, the key mechanisms that promote dispersal are difficult to identify and remain unclear for most free-living organisms. Inbreeding avoidance is commonly invoked as a major driver of dispersal, but inbreeding can also be favoured by kin selection if inbred mating increases the inclusive fitness of the parents. Here, we investigated the relationships between inbreeding, kinship, sex and dispersal propensity in a carefully monitored population of captive-bred North African houbara bustards, Chlamydotis undulata , in Morocco. Over 8 years, 79 houbaras (of known pedigree) were released into the wild and radiotracked over a large spatial scale until settlement. Using several dispersal metrics, we confirmed that both inbreeding and kinship affect dispersal, with differential effects depending on sex. In males, settlement distance was associated with movements soon after release, whereas in females, later movements determined settlement distance. When released with close kin, females in female-biased release groups covered greater distances than when released with distant kin, suggesting that intrasexual kin competition governs dispersal in females. In males, dispersal was reduced when associated with genetically close relatives but increased with the individual coefficient of inbreeding. Overall, our results highlight complex (but consistent with theoretical expectations) sex differences in movement patterns that depend on inbreeding, kinship, group structure, type of movement and stage of the dispersal process.