ARE THERE DIFFERENCES IN FITNESS COMPONENTS BETWEEN PHILOPATRIC AND DISPERSING INDIVIDUALS

Estimates of fitness associated with dispersal and philopatry are need ed if we are to evaluate their evolution and their demographic consequ ences. We examine previous theory, the main types of study design and review available data on the relative fitnesses of dispersing and phil opatric individuals. Transience and settlement are usually costly for dispersers, but after settlement, dispersers have both advantages and disadvantages when compared to philopatric individuals. Moreover, we o bserved compensation between components of fitness. Intraspecific vari ability associated with sex was frequent, but variability over time, s pace or dispersal type were rarely studied. Finally, we found that pot ential effects were commonly confounded. Transience has been studied i n mammals, and for natal dispersal only. The consequences of breeding dispersal have been documented only in birds. After natal dispersal, f ecundity has been the subject of most comparisons in birds. Finally we propose an experimental design which may help in separating the effec t of dispersal type from an area effect.