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 (Turdus lherminieri), 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 km. 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 (Fst from 0.073–0.153), 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 in situ, 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，具移动能力的生物仅在较大地理距离范围内才会出现种群分化。然而，越来越多的研究证据表明，物种的扩散潜力与实际基因流之间存在偏差。本研究报道了小安的列斯群岛特有鸟类——林鸫（Turdus lherminieri）在极小空间尺度下呈现的引人关注的分化模式。对分布于3个岛屿的17个采样点的331个个体进行分析后发现，这3个被40至50公里海域分隔的岛屿之间存在显著的形态与遗传分化。更为意外的是，我们在瓜德罗普岛的两个地理区域间发现，表型分化与极强的遗传分化（Fst值介于0.073至0.153之间）显著相关；考虑到其极小的空间尺度，该模式在鸟类研究中实属罕见。分子数据分析（包括线粒体控制区序列与微卫星基因型）表明，这种强烈的分化可能为原位发生，但其他备选假说尚未被完全排除。本研究提示，当前持续发生的生境破碎化（尤其在热带森林中）对鸟类种群的影响可能远超此前的预期。