Rates of phenotypic change are greater in cities than in any other habitat. Consequently, urban habitats are an ideal experimental area to study contemporary evolution and adaptation. A key question related to phenotypic changes in urban animals relates to the patterns of gene flow between the city and the natural habitats surrounding cities, but the results obtained thus far have been contradictory. The aim of this study was to analyze genetic differentiation and patterns of gene flow and size variation in urban blue tits Cyanistes caeruleus in Barcelona city, using a panel of 26 microsatellites. We compared birds from one locality at the city center, one at the suburban area, and one in a nearby forest. We found a significant genetic differentiation between the populations, which has evolved over a period of about 35 generations (50 years), based on historical data. There was significant gene flow between all populations. There was no significant asymmetric gene flow between the forest and the other two populations, which is consistent with balanced gene flow and dispersal. City birds were smaller than individuals from the forest. Simulations showed that the selection required to achieve these phenotypic differences would have to be high, which in turn suggests that phenotype-dependent dispersal may be involved.

中文翻译：

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最近蓝山雀在巴塞罗那城市环境中的传播：形态差异和平衡分散的作用

城市的表型变化率高于任何其他栖息地。因此，城市栖息地是研究当代进化和适应的理想实验区。与城市动物表型变化有关的一个关键问题与城市与城市周围自然栖息地之间的基因流动模式有关，但迄今为止获得的结果相互矛盾。本研究的目的是使用一组 26 颗微卫星分析巴塞罗那市城市蓝山雀 Cyanistes caeruleus 的遗传分化和基因流模式以及大小变异。我们比较了市中心一个地方、郊区的一只和附近森林中的一只鸟。我们发现种群之间存在显着的遗传差异，这种差异已经进化了大约 35 代（50 年），根据历史数据。所有种群之间存在显着的基因流动。森林与其他两个种群之间没有显着的不对称基因流动，这与平衡的基因流动和扩散是一致的。城市鸟类比森林中的个体小。模拟表明，实现这些表型差异所需的选择必须很高，这反过来表明可能涉及表型依赖性扩散。