Abstract
BackgroundMetapopulation persistence in fragmented landscapes is assured by dispersal of individuals between local populations. In this scenario the landscape topography, although usually neglected, may have an important role in shaping dispersal throughout the matrix separating habitat patches. Due to inter-sexual differences in optimal reproductive strategies, i.e., males maximizing the number of mating opportunities and females maximizing the offspring survival chances, topography-related constraints are expected to exert a different effect on male and female dispersal behaviour. We tested sex-biased topography effects on butterfly dispersal, with the following hypotheses: (1) females are constrained by topography in their movements and avoid hill crossing; (2) male dispersal is primarily driven by two-dimensional spatial structure of the habitat patches (i.e. their geometric locations and sizes) and little influenced by topography.MethodsFollowing intensive mark-recapture surveys of Maculinea (= Phengaris) nausithous and M. teleius within a landscape characterised by an alternation of hills and valleys, we investigated sex-specific patterns in their inter-patch movement probabilities derived with a multi-state recapture model. In particular, we (1) analysed the fit of dispersal kernels based on Euclidean (= straight line) vs. topography-based (= through valley) distances; (2) compared movement probabilities for the pairs of patches separated or not by topographic barriers; and (3) tested the differences in the downward and upward movement probabilities within the pairs of patches.ResultsEuclidean distances between patches proved to be a substantially stronger predictor of inter-patch movement probabilities in males, while inter-patch distances measured along valleys performed much better for females, indicating that the latter tend to predominantly follow valleys when dispersing. In addition, there were significantly lower probabilities of movements across hills in females, but not in males.ConclusionsBoth above results provide support for the hypothesis that topography restricts dispersal in females, but not in males. Since the two sexes contribute differently to metapopulation functioning, i.e., only female dispersal can result in successful (re)colonisations of vacant patches, the topography effects exerted on females should be considered with particular attention when landscape management and conservation actions are designed in order to maintain the functional connectivity of metapopulation systems.
Highlights
Metapopulation persistence in fragmented landscapes is assured by dispersal of individuals between local populations
We tested the following hypotheses: (1) females are constrained by topography in their movements and avoid hill crossing; (2) male dispersal is primarily driven by two-dimensional spatial structure of the habitat patches and little influenced by topography
The inter-patch movement probabilities estimated with the multi-state recapture model ranged from 0 to slightly above 12%, in most cases they were below 3%
Summary
Metapopulation persistence in fragmented landscapes is assured by dispersal of individuals between local populations. In this scenario the landscape topography, usually neglected, may have an important role in shaping dispersal throughout the matrix separating habitat patches. Dispersal may help to avoid inbreeding and reduce competition for resources and mates, thereby increasing individual fitness [39]. There is a relatively high mortality risk during the movement from natal sites to new areas mainly due to the lack of resources or unfavourable conditions in the matrix separating habitat patches [30, 86]. Having reached a target site, dispersers may suffer reduced survival or lower reproductive success because of difficulties in resettling in a novel environment (e.g. [15, 46])
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