Abstract
Habitat specialists inhabiting scarce and scattered habitat patches pose interesting questions related to dispersal such as how specialized terrestrial mammals do to colonize distant patches crossing hostile matrices. We assess dispersal patterns of the southern water vole (Arvicola sapidus), a habitat specialist whose habitat patches are distributed through less than 2% of the study area (overall 600 km2) and whose populations form a dynamic metapopulational network. We predict that individuals will require a high ability to move through the inhospitable matrix in order to avoid genetic and demographic isolations. Genotypes (N = 142) for 10 microsatellites and sequences of the whole mitochondrial Control Region (N = 47) from seven localities revealed a weak but significant genetic structure partially explained by geographic distance. None of the landscape models had a significant effect on genetic structure over that of the Euclidean distance alone and no evidence for efficient barriers to dispersal was found. Contemporary gene flow was not severely limited for A. sapidus as shown by high migration rates estimates (>10%) between non-neighbouring areas. Sex-biased dispersal tests did not support differences in dispersal rates, as shown by similar average axial parent-offspring distances, in close agreement with capture-mark-recapture estimates. As predicted, our results do not support any preferences of the species for specific landscape attributes on their dispersal pathways. Here, we combine field and molecular data to illustrate how a habitat specialist mammal might disperse like a habitat generalist, acquiring specific long-distance dispersal strategies as an adaptation to patchy, naturally fragmented, heterogeneous and unstable habitats.
Highlights
Animal dispersal is commonly defined as the movement of individuals away from their home ranges with no subsequent return [1]
Dispersal of Arvicola sapidus Our results provide the first insight into the genetic structure and patterns of gene flow of Southern water voles in a Mediterranean patchy habitat
We found a moderate level of population genetic diversity, slightly lower than that previously reported in metapopulations of European water voles (Arvicola terrestris) [15]
Summary
Animal dispersal is commonly defined as the movement of individuals away from their home ranges with no subsequent return (at least, temporally) [1]. Individuals disperse as an effective strategy for the avoidance of inbreeding, resource competition, and kin competition [2], and this initiates important ecological and genetic feedbacks in spatially structured populations [3]. In naturally or anthropogenically fragmented landscapes, the degree of fragmentation and the spatial configuration of the network of patches will influence dispersal routes and probabilities and, will affect the rates of colonization of empty patches and the distribution of genetic diversity [7]. These consequences make of dispersal a keystone process in ecological and evolutionary studies. Dispersal may be seen as the glue that holds populations connected, and as the glue that connects different scales and disciplines [8]
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