Data from: A century of genetic change and metapopulation dynamics in the Galápagos warbler finches (Certhidea)

Populations that are connected by immigrants play an important role in evolutionary and conservation biology, yet we have little direct evidence of how such metapopulations change genetically over evolutionary time. We compared historic (1895-1905) to modern (1988-2006) genetic variation in 11 populations of warbler finches at 14 microsatellite loci. Although several lines of evidence suggest that Darwin’s finches may be in decline, we found that the genetic diversity of warbler finches has not generally declined, and broad scale patterns of variation remained similar over time. Contrary to expectations, inferred population sizes have generally increased over time (6-8%) as have immigration rates (8-16%), which may reflect a recent increase in the frequency and intensity of El Niño events. Individual island populations showed significant declines (18-19%) and also substantial gains (18-20%) in allelic richness over time. Changes in genetic diversity were correlated with changes in immigration rates, but did not correspond to population size or human disturbance. These results reflect the expected stabilizing properties of whole metapopulations over time. However, the dramatic and unpredictable changes observed in individual populations during this short time interval suggests that care should be taken when monitoring individual population fragments with snapshots of genetic variation.

通过移民事件实现连通的种群在进化生物学与保护生物学领域具有重要研究价值，但目前学界对这类集合种群（metapopulation）在进化尺度上的遗传变化模式仍缺乏直接实证支撑。本研究针对11个莺雀种群的14个微卫星位点（microsatellite loci），对比了其历史样本（1895-1905年）与现代样本（1988-2006年）的遗传变异特征。尽管多项证据显示达尔文雀（Darwin’s finches）种群或已出现衰退，但本研究发现莺雀的遗传多样性整体并未出现下降，且其遗传变异的宏观格局随时间推移未发生显著改变。与预期相悖的是，推算得到的种群规模整体提升了6%-8%，移民率亦增长了8%-16%，这一现象或与近期厄尔尼诺（El Niño）事件的发生频率与强度增加相关。单个岛屿种群的等位基因丰富度（allelic richness）则随时间推移呈现出显著下降（18%-19%）与显著提升（18%-20%）两种截然相反的变化。遗传多样性的变化与移民率的改变呈显著相关，但与种群规模或人类干扰程度并无对应关系。上述结果印证了集合种群随时间推移应具备的稳定特性。然而，在这一较短的时间跨度内，单个岛屿种群所呈现出的剧烈且不可预测的变化提示我们，在通过遗传变异快照监测单个种群片段时需格外审慎。