Data from: Variation in fine-scale genetic structure and local dispersal patterns between peripheral populations of a South American passerine bird

The distribution of suitable habitat influences natal and breeding dispersal at small spatial scales, resulting in strong micro-geographic genetic structure. Although environmental variation can promote inter-population differences in dispersal behavior and local spatial patterns, the effects of distinct ecological conditions on within-species variation in dispersal strategies and in fine-scale genetic structure remain poorly understood. We studied local dispersal and fine-scale genetic structure in the thorn-tailed rayadito (Aphrastura spinicauda), a South American bird that breeds along a wide latitudinal gradient. We combine capture-mark-recapture data from eight breeding seasons and molecular genetics to compare two peripheral populations with contrasting environments in Chile: Navarino Island, a continuous and low density habitat, and Fray Jorge National Park, a fragmented, densely populated and more stressful environment. Natal dispersal showed no sex bias in Navarino, but was female-biased in the more dense population in Fray Jorge. In the latter, male movements were restricted and some birds seemed to skip breeding in their first year, suggesting habitat saturation. Breeding dispersal was limited in both populations, with males being more philopatric than females. Spatial genetic autocorrelation analyses using 13 polymorphic microsatellite loci confirmed the observed dispersal patterns: a fine-scale genetic structure was only detectable for males in Fray Jorge for distances up to 450 m. Furthermore, two-dimensional autocorrelation analyses and estimates of genetic relatedness indicated that related males tended to be spatially clustered in this population. Our study shows evidence for context-dependent variation in natal dispersal and corresponding local genetic structure in peripheral populations of this bird. It seems likely that the costs of dispersal are higher in the fragmented and higher density environment in Fray Jorge, particularly for males. The observed differences in micro-geographic genetic structure for rayaditos might reflect the genetic consequences of population-specific responses to contrasting environmental pressures near the range limits of its distribution.适宜生境的分布格局会在小空间尺度上影响个体的出生扩散（natal dispersal）与繁殖扩散（breeding dispersal），进而形成显著的微观地理遗传结构（micro-geographic genetic structure）。尽管环境异质性可推动种群间扩散行为与局域空间格局的分化，但迥异的生态条件如何影响同物种种内扩散策略与精细尺度遗传结构（fine-scale genetic structure）的变异，目前仍有待深入阐明。 本研究以沿宽广纬度梯度繁殖的南美鸟类棘尾雷雀（thorn-tailed rayadito，学名*Aphrastura spinicauda*）为研究对象，探讨其局域扩散与精细尺度遗传结构。本研究整合了8个繁殖季的标记重捕法（capture-mark-recapture）数据与分子遗传学数据，对智利境内两处环境迥异的边缘种群开展对比研究：一处是生境连续且种群密度较低的纳瓦里诺岛种群，另一处则是生境破碎化、种群密度偏高且生存压力更大的弗雷豪尔赫国家公园种群。 纳瓦里诺岛种群的出生扩散无显著性别偏向性，而弗雷豪尔赫国家公园的高密度种群则表现出雌性偏向的出生扩散模式。在后一种群中，雄性的扩散活动受到限制，部分个体似乎会跳过首年繁殖，这暗示生境已达到饱和状态。两处种群的繁殖扩散均较为有限，且雄性相较于雌性表现出更强的恋巢性（philopatry）。 基于13个多态性微卫星位点（microsatellite loci）的空间遗传自相关分析（spatial genetic autocorrelation analyses）验证了观测到的扩散模式：仅在弗雷豪尔赫国家公园种群中，雄性个体在450米以内的空间尺度上呈现出精细尺度遗传结构。此外，二维自相关分析与遗传亲缘关系估算结果表明，该种群内亲缘关系较近的雄性个体往往在空间上呈现聚集分布。 本研究证实，该鸟类边缘种群的出生扩散存在环境依赖型变异，且与之对应的局域遗传结构亦存在相应分化。由此推测，在生境破碎化且种群密度偏高的弗雷豪尔赫国家公园，尤其是雄性个体，扩散的代价更高。本次研究观测到的棘尾雷雀微观地理遗传结构差异，或可反映该物种种群在分布范围边缘针对迥异环境压力产生的种群特异性响应所带来的遗传效应。