The enduring question of sex-biased dispersal: Paul J. Greenwood's (1980) seminal contribution

In 1980, Paul J. Greenwood published a review of dispersal in birds and mammals that has been widely cited. The review evaluated possible explanations for sex-biased natal dispersal. It concluded that female-biased dispersal occurred in socially monogamous birds because males were using territorial resources to attract mates. In mammals, polygynous and polygynandrous males compete directly for and defend groups of females, and thus males more often disperse to find opportunities to sequester such groups. Thus, the primary difference between birds and mammals in sex-bias of dispersal appeared to be one of resource defence and mate defence mating systems. What made this review so seminal and what is the fate of his research question today? I begin with the excitement of the 'sociobiology' revolution and the fundamental nature and importance of the topic of dispersal. Furthermore, as all living things disperse, the topic of dispersal is central to many fields of study in behaviour, ecology, conservation and evolutionary biology. The hypotheses to explain dispersal that Greenwood reviewed (competition for resources, competition for mates and inbreeding avoidance) have been augmented, primarily by interest in lowered local kin competition as a fitness advantage for dispersers and kin cooperation as a reason not to disperse (viz. to remain philopatric in or near the natal area, particularly for female mammals). Current studies of Greenwood's question about sex biases in dispersal focus on testing the effects of local kin competition and on phylogenetic comparisons that reveal evidence of independent evolution of alternative dispersal patterns. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.