Department of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, CA 90095, United States.
Escuela de Biología, Pontificia Universidad Católica del Ecuador, Av. 12 de Octubre, Quito 170901, Ecuador.
J Hered. 2024 Jul 10;115(4):444-457. doi: 10.1093/jhered/esae017.
Similar to other insular birds around the world, the Galapagos rail (Laterallus spilonota Gould, 1841) exhibits reduced flight capacity following its colonization of the archipelago ~1.2 mya. Despite their short evolutionary history, rails have colonized seven different islands spanning the entire width of the archipelago. Galapagos rails were once common on islands with sufficiently high altitudes to support shrubs in humid habitats. After humans introduced goats, this habitat was severely reduced due to overgrazing. Habitat loss devastated some rail populations, with less than 50 individuals surviving, rendering the genetic diversity of Galapagos rail a pressing conservation concern. Additionally, one enigma is the reappearance of rails on the island of Pinta after they were considered extirpated. Our approach was to investigate the evolutionary history and geographic distribution of Galapagos rails as well as examine the genome-wide effects of historical population bottlenecks using 39 whole genomes across different island populations. We recovered an early divergence of rail ancestors leading to the isolated populations on Pinta and a second clade comprising the rest of the islands, historically forming a single landmass. Subsequently, the separation of the landmass ~900 kya may have led to the isolation of the Isabela population with more panmictic populations found on Santa Cruz and Santiago islands. We found that rails genomes contain long runs of homozygosity (>2 Mb) that could be related to the introduction of goats. Finally, our findings show that the modern eradication of goats was critical to avoiding episodes of inbreeding in most populations.
与世界上其他岛屿鸟类相似，加拉帕戈斯秧鸡（Laterallus spilonota Gould, 1841）在大约 120 万年前殖民该群岛后，飞行能力下降。尽管它们的进化历史很短，但秧鸡已经在跨越群岛全长的七个不同岛屿上进行了殖民。加拉帕戈斯秧鸡曾经在海拔足够高、有灌木的岛屿上很常见，生活在潮湿的栖息地。人类引入山羊后，由于过度放牧，这种栖息地严重减少。栖息地的丧失使一些秧鸡种群遭受重创，幸存的个体不到 50 只，这使得加拉帕戈斯秧鸡的遗传多样性成为一个紧迫的保护问题。此外，一个谜是秧鸡在被认为灭绝的平塔岛再次出现。我们的方法是调查加拉帕戈斯秧鸡的进化历史和地理分布，利用不同岛屿种群的 39 个全基因组研究历史人口瓶颈对基因组范围的影响。我们发现秧鸡祖先的早期分化导致了平塔岛的孤立种群和第二组群，包括其余岛屿，历史上形成了一个单一的大陆块。随后，大约 900 万年前大陆块的分离可能导致了伊莎贝拉种群的隔离，而在圣克鲁斯岛和圣地亚哥岛发现了更多的混合种群。我们发现秧鸡的基因组含有长段的纯合性（>2 Mb），这可能与山羊的引入有关。最后，我们的研究结果表明，现代山羊的灭绝对避免大多数种群的近交至关重要。
