Metapopulation 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. Following 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. Euclidean 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. Both 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.

中文翻译：

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性别偏向对蝴蝶扩散的影响

个体分散在当地人口中可以确保零散景观中的种群持续存在。在这种情况下，景观地形虽然通常会被忽略，但可能在整个分散生境斑块的矩阵中形成扩散方面起着重要作用。由于最佳生殖策略的两性差异，即雄性最大化了交配机会的数量，雌性最大化了后代的生存机会，预计与地形相关的限制对雄性和雌性的传播行为会产生不同的影响。我们用以下假设测试了偏向性地形对蝴蝶散布的影响：（1）雌性的运动受到地形的限制，避免越过山坡；（2）雄性扩散主要是由栖息地斑块的二维空间结构（即它们的几何位置和大小）驱动的，而不受地形的影响很小。在对以丘陵和山谷交替为特征的景观中的Maculinea（= Phengaris）恶臭和斜纹夜蛾进行密集的标记捕获调查之后，我们研究了通过多状态捕获模型得出的斑块间移动概率中的性别特定模式。特别是，我们（1）分析了基于欧几里得（=直线）与基于地形的（=穿过山谷）距离的散布核的拟合；（2）比较了被地形障碍分开或未分开的成对斑块的移动概率；（3）测试了成对补丁中向下和向上移动概率的差异。斑块之间的欧几里得距离被证明是雄性斑块间移动概率的明显更强的预测指标，而沿着谷地测量的斑块间距离对雌性则要好得多，这表明在分散时，后者往往主要跟随谷点。此外，女性（而非男性）跨山运动的概率明显较低。以上两个结果都支持以下假设：地形限制了女性的散布，但男性没有散布。由于这两种性别对代谢种群功能的贡献不同，也就是说，只有女性散布才能导致空位的成功定殖（重新定殖），