Dispersal in bank voles: benefits to emigrants or to residents?

Abstract

Revises the recent hypotheses on the evolution of dispersal behaviour in voles, namely Emigrant Fitness Hypothesis (EFH) versus Resident Fitness Hypothesis (RFH), on the basis of 3-yr study on dispersal of Clethrionomys glareolus. The studied populations lived in a small island, a rich alder forest (both optimal habitats) and small patches of woods (suboptimal habitat). Young voles born in the first litters of the year commonly dispersed from the optimal natal habitat into the vacant suboptimal habitat. These immigrants had higher reproductive success in the new habitat than their counterparts in the control habitat. Residents, which were parents and younger siblings of emigrants, also benefited from the absence of dispersers: their home ranges were less crowded and food depleted, and the rates of maturation were higher than in the control habitat. The gain in the inclusive fitness of matrilines with dispersing young is postulated as a ultimate cause for dispersal. A mutual overlap in predictions of EFH and RFH is indicated. -from Author