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可在小空间尺度上调控鸟类的出生扩散与繁殖扩散过程，进而形成显著的微地理遗传结构。尽管环境异质性可推动不同种群间扩散行为与局域空间格局的分化，但针对不同生态条件如何作用于同物种种内扩散策略变异及精细尺度遗传结构的相关研究仍知之甚少。我们以棘尾雷雀（thorn-tailed rayadito，学名*Aphrastura spinicauda*）为研究对象，该物种为南美鸟类，繁殖范围覆盖广阔的纬度梯度。我们结合8个繁殖季的标记重捕（capture-mark-recapture）数据与分子遗传学数据，对智利境内两个环境迥异的边缘种群展开对比研究：一处为纳瓦里诺岛，其生境连续且种群密度较低；另一处为弗雷豪尔赫国家公园，该区域生境破碎化、种群密度偏高且环境胁迫更强。纳瓦里诺岛种群的出生扩散无明显性偏倚，而弗雷豪尔赫高密度种群的出生扩散则表现为雌性偏倚。在弗雷豪尔赫种群中，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。两个种群的繁殖扩散均较为有限，且雄性的恋巢性均强于雌性。我们利用13个多态性微卫星位点（microsatellite loci）开展空间遗传自相关分析，验证了观测到的扩散模式：仅在弗雷豪尔赫种群的雄性个体中，当空间距离不超过450米时，可检测到精细尺度的遗传结构。此外，二维自相关分析与遗传相关度估算结果显示，该种群中亲缘关系较近的雄性个体往往在空间上呈聚集分布。我们的研究证实，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差异。由此推测，在弗雷豪尔赫的破碎化高密度生境中，扩散的代价更高，对雄性个体而言尤为如此。本次研究观测到的棘尾雷雀微地理遗传结构差异，或反映了该物种在分布范围边界附近，不同种群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。