Data from: Morphology and genetics reveal an intriguing pattern of differentiation at a very small geographic scale in a bird species, the forest thrush Turdus lherminieri

Mobile organisms are expected to show population differentiation only over fairly large geographical distances. However, there is growing evidence of discrepancy between dispersal potential and realized gene flow. Here we report an intriguing pattern of differentiation at a very small spatial scale in the forest thrush (<i>Turdus lherminieri</i>), a bird species endemic to the Lesser Antilles. Analysis of 331 individuals from 17 sampling sites distributed over three islands revealed a clear morphological and genetic differentiation between these islands isolated by 40-50 kilometers. More surprisingly, we found that the phenotypic divergence between the two geographic zones of the island of Guadeloupe was associated with a very strong genetic differentiation (<i>F</i>_st from 0.073 to 0.153), making this pattern a remarkable case in birds given the very small spatial scale considered. Molecular data (mitochondrial control region sequences and microsatellite genotypes) suggest that this strong differentiation could have occurred <i>in situ</i>, although alternative hypotheses cannot be fully discarded. This study suggests that the ongoing habitat fragmentation, especially in tropical forests, may have a deeper impact than previously thought on avian populations.

通常认为，具有移动能力的生物仅会在较大地理距离范围内出现种群分化。然而，越来越多的证据表明，生物的扩散潜力与实际基因流之间存在不一致性。本研究报道了小安的列斯群岛特有鸟类——安的列斯林鸫（*Turdus lherminieri*）在极小空间尺度下出现的引人关注的分化模式。对分布于3座岛屿的17个采样点的331个个体进行分析后发现，这三座被40至50公里海水隔离的岛屿种群间存在显著的形态与遗传分化。更令人意外的是，研究团队在瓜德罗普岛的两个地理区域间发现了表型分化与极强的遗传分化（F_st值介于0.073至0.153之间）相关联的现象，考虑到其极小的空间尺度，这一模式在鸟类研究中堪称罕见案例。分子数据（线粒体控制区序列与微卫星基因型）显示，这种强烈的分化大概率是原地发生的，不过其他替代假说仍无法完全排除。本研究表明，当前持续进行的生境破碎化（尤其是热带森林生境破碎化）对鸟类种群的影响可能远超此前的认知。