Inbreeding avoidance and male-biased natal dispersal in Antechinus spp. (Marsupialia: Dasyuridae)

Circumstantial and experimental evidence suggests that the benefits of inbreeding avoidance are a sufficient cause for the evolution of sex-biased dispersal in dasyurid marsupial genus Antechinus, and alternative causes are inadequate because of the absence of a class of experienced males that would promote dispersal among subordinates.

Abstract

Members of the dasyurid marsupial genus Antechinus and their close relatives are unique among terrestrial vertebrates because male generations are discrete, being punctuated by an abrupt post-mating mortality. Amost all juvenile males disperse shortly after they are weaned, while females are strongly philopatric. Circumstantial and experimental evidence suggests that mothers cause the dispersal of their sons and recruit unrelated males to live with themselves and their daughters during this dispersal phase. Dispersal generally involves all the males in a litter and occurs in litters with a single male, those consisting entirely of males, and even where the mother will not breed again. These data suggest the benefits of inbreeding avoidance are a sufficient cause for the evolution of sex-biased dispersal. Alternative causes that have been suggested in the literature are inadequate because of the absence of a class of experienced males that would promote dispersal among subordinates, and the failure of the dispersal to reduce group-size in nests.