Kearns Anna M, Campana Michael G, Slikas Beth, Berry Lainie, Saitoh Takema, Cibois Alice, Fleischer Robert C
Center for Conservation Genomics, Smithsonian's National Zoological Park and Conservation Biology Institute, Washington, District of Columbia, USA.
Department of Lands and Natural Resources, Commonwealth of the Northern Mariana Islands, Saipan, Northern Mariana Islands.
Mol Ecol. 2022 Apr;31(7):1995-2012. doi: 10.1111/mec.16382. Epub 2022 Feb 16.
Conservation benefits from incorporating genomics to explore the impacts of population declines, inbreeding, loss of genetic variation and hybridization. Here we use the near-extinct Mariana Islands reedwarbler radiation to showcase how ancient DNA approaches can allow insights into the population dynamics of extinct species and threatened populations for which historical museum specimens or material with low DNA yield (e.g., scats, feathers) are the only sources for DNA. Despite their having paraphyletic mitochondrial DNA (mtDNA), nuclear single nucleotide polymorphisms (SNPs) support the distinctiveness of critically endangered Acrocephalus hiwae and the other three species in the radiation that went extinct between the 1960s and 1990s. Two extinct species, A. yamashinae and A. luscinius, were deeply divergent from each other and from a third less differentiated lineage containing A. hiwae and extinct A. nijoi. Both mtDNA and SNPs suggest that the two isolated populations of A. hiwae from Saipan and Alamagan Islands are sufficiently distinct to warrant subspecies recognition and separate conservation management. We detected no significant differences in genetic diversity or inbreeding between Saipan and Alamagan, nor strong signatures of geographical structuring within either island. However, the implications of possible signatures of inbreeding in both Saipan and Alamagan, and long-term population declines in A. hiwae that pre-date modern anthropogenic threats require further study with denser population sampling. Our study highlights the value that conservation genomics studies of island radiations have as windows onto the possible future for the world's biota as climate change and habitat destruction increasingly fragment their ranges and contribute to rapid declines in population abundances.
将基因组学纳入研究范畴，有助于探索种群数量下降、近亲繁殖、遗传变异丧失和杂交所带来的影响，从而实现生物多样性的保护。在此，我们以濒临灭绝的马里亚纳群岛苇莺辐射种群为例，展示古代DNA方法如何让我们深入了解灭绝物种和受威胁种群的种群动态，对于这些物种而言，历史博物馆标本或DNA产量低的材料（如粪便、羽毛）是唯一的DNA来源。尽管它们的线粒体DNA（mtDNA）呈并系发生，但核单核苷酸多态性（SNP）支持极度濒危的希瓦苇莺（Acrocephalus hiwae）以及在20世纪60年代至90年代间灭绝的辐射种群中的其他三个物种的独特性。两个已灭绝物种，山阶苇莺（A. yamashinae）和乌卢甘苇莺（A. luscinius），彼此之间以及与包含希瓦苇莺和已灭绝的尼霍伊苇莺（A. nijoi）的第三个分化程度较低的谱系之间差异很大。线粒体DNA和SNP均表明，来自塞班岛和阿拉马甘岛的两个孤立的希瓦苇莺种群差异显著，足以认定为亚种并进行单独的保护管理。我们未检测到塞班岛和阿拉马甘岛在遗传多样性或近亲繁殖方面存在显著差异，也未发现任一岛屿内部存在强烈的地理结构特征。然而，塞班岛和阿拉马甘岛可能存在的近亲繁殖特征以及希瓦苇莺在现代人为威胁之前就已出现的长期种群数量下降的影响，需要通过更密集的种群采样进行进一步研究。我们的研究强调了对岛屿辐射种群进行保护基因组学研究的价值，这些研究就像一扇窗，让我们得以窥见世界生物群可能的未来，因为气候变化和栖息地破坏正日益使其分布范围碎片化，并导致种群数量迅速减少。
