Data from: Sex-specific estimates of dispersal show female philopatry and male dispersal in a promiscuous amphibian, the alpine salamander (Salamandra atra)

Amphibians display wide variations in life-history traits and life cycles that should prove useful to explore the evolution of sex-biased dispersal, but quantitative data on sex-specific dispersal patterns are scarce. Here we focused on Salamandra atra, an endemic alpine species showing peculiar life-history traits. Strictly terrestrial and viviparous, the species has a promiscuous mating system and females reproduce only every three to four years. In the present study, we provide quantitative estimates of asymmetries in male vs female dispersal using both field-based (mark-recapture) and genetic approaches (detection of sex-biased dispersal and estimates of migration rates based on the contrast in genetic structure across sexes and age classes). Our results revealed a high level of gene flow among populations, which stems exclusively from male dispersal. We hypothesize that philopatric females benefit from being familiar with their natal area for the acquisition and defence of an appropriate shelter, while male dispersal has been secondarily favoured by inbreeding avoidance. Together with other studies on amphibians, our results indicate that a species' mating system alone is a poor predictor of sex-linked differences in dispersal, in particular for promiscuous species. Further studies should focus more directly on the proximate forces that favour or limit dispersal to refine our understanding of the evolution of sex-biased dispersal in animals.

两栖类展现出丰富多样的生活史特征与生命周期变异，本可作为探究性偏扩散（sex-biased dispersal）演化的理想研究体系，但目前关于性特异性扩散模式的定量研究数据仍较为匮乏。本研究聚焦于阿尔卑斯山特有物种Salamandra atra，该物种具有独特的生活史特征：为严格陆生的胎生（viviparous）物种，婚配制度为混杂交配（promiscuous mating system），且雌性每3至4年才繁殖一次。本研究同时采用野外标记重捕法（mark-recapture）与遗传学分析手段，对雌雄个体间的扩散不对称性开展定量估算：其中遗传学分析通过比较不同性别及年龄组的遗传结构（genetic structure）差异，实现了性偏扩散的检测与迁移率（migration rate）估算。研究结果显示，种群间存在高水平的基因流（gene flow），且该基因流完全源自雄性个体的扩散。我们据此提出假说：具有恋巢性（philopatry）的雌性可通过熟悉出生地环境，更高效地获取并守护适宜的庇护所；而雄性扩散则因近交回避（inbreeding avoidance）的选择压力得到了次生演化青睐。结合其他两栖类相关研究，本研究结果表明，仅依靠物种的婚配制度无法准确预测扩散行为的性别关联差异，对于混杂交配物种而言尤其如此。未来研究应更直接地聚焦于调控扩散行为的近因性选择压力，以深化我们对动物性偏扩散演化机制的理解。