Smithsonian Conservation Biology Institute, Center for Conservation and Evolutionary Genetics, National Zoological Park, Washington, DC, USA.
Mol Biol Evol. 2012 Dec;29(12):3729-40. doi: 10.1093/molbev/mss185. Epub 2012 Jul 25.
In the Hawaiian Islands, human colonization, which began approximately 1,200 to 800 years ago, marks the beginning of a period in which nearly 75% of the endemic avifauna became extinct and the population size and range of many additional species declined. It remains unclear why some species persisted whereas others did not. The endemic Hawaiian petrel (Pterodroma sandwichensis) has escaped extinction, but colonies on two islands have been extirpated and populations on remaining islands have contracted. We obtained mitochondrial DNA sequences from 100 subfossil bones, 28 museum specimens, and 289 modern samples to investigate patterns of gene flow and temporal changes in the genetic diversity of this endangered species over the last 3,000 years, as Polynesians and then Europeans colonized the Hawaiian Islands. Genetic differentiation was found to be high between both modern and ancient petrel populations. However, gene flow was substantial between the extirpated colonies on Oahu and Molokai and modern birds from the island of Lanai. No significant reductions in genetic diversity occurred over this period, despite fears in the mid-1900s that this species may have been extinct. Simulations show that even a decline to a stable effective population size of 100 individuals would result in the loss of only 5% of the expected heterozygosity. Simulations also show that high levels of genetic diversity may be retained due to the long generation time of this species. Such decoupling between population size and genetic diversity in long-lived species can have important conservation implications. It appears that a pattern of dispersal from declining colonies, in addition to long generation time, may have allowed the Hawaiian petrel to escape a severe genetic bottleneck, and the associated extinction vortex, and persist despite a large population decline after human colonization.
在夏威夷群岛，人类的殖民活动始于大约 1200 至 800 年前，标志着一个时期的开始，在此期间，近 75%的特有鸟类灭绝，许多其他物种的种群规模和范围缩小。目前还不清楚为什么有些物种能够幸存下来，而有些则不能。夏威夷海燕（Pterodroma sandwichensis）这种特有物种逃脱了灭绝的命运，但两个岛屿上的繁殖地已经消失，其余岛屿上的种群也在减少。我们从 100 块化石骨骼、28 件博物馆标本和 289 个现代样本中获得了线粒体 DNA 序列，以研究在过去 3000 年中，波利尼西亚人和后来的欧洲人殖民夏威夷群岛期间，这种濒危物种的基因流动模式和遗传多样性的时间变化。现代和古代海燕种群之间的遗传分化程度很高。然而，在瓦胡岛和莫洛凯岛灭绝的繁殖地与拉奈岛的现代鸟类之间，基因流动是大量的。尽管在 20 世纪中期有人担心这个物种可能已经灭绝，但在此期间，遗传多样性并没有显著减少。模拟表明，即使这个物种的有效种群数量下降到一个稳定的 100 只个体，也只会导致预期杂合度损失 5%。模拟还表明，由于该物种的世代时间较长，可能会保留高水平的遗传多样性。在长寿物种中，种群规模和遗传多样性之间的这种脱钩可能具有重要的保护意义。看来，除了世代时间长之外，从衰落的繁殖地扩散的模式可能使夏威夷海燕逃脱了严重的遗传瓶颈和相关的灭绝漩涡，并在人类殖民后种群大量减少的情况下得以幸存。
