Bunce Michael, Worthy Trevor H, Ford Tom, Hoppitt Will, Willerslev Eske, Drummond Alexei, Cooper Alan
Henry Wellcome Ancient Biomolecules Centre, Department of Zoology, University of Oxford, Oxford OX1 3PS, UK.
Nature. 2003 Sep 11;425(6954):172-5. doi: 10.1038/nature01871.
The ratite moa (Aves; Dinornithiformes) were massive graviportal browsers weighing up to 250 kg (ref. 1) that dominated the New Zealand biota until their extinction approximately 500 yr ago. Despite an extensive Quaternary fossil record, moa taxonomy remains problematic and currently 11 species are recognized. Three Dinornis species were found throughout New Zealand and differed markedly in size (1-2 m height at back) and mass (from approximately 34 to 242 kg). Surprisingly, ancient mitochondrial DNA sequences show that the three species were genetically indistinguishable within each island, but formed separate North and South Island clades. Here we show, using the first sex-linked nuclear sequences from an extinct species, that on each island the three morphological forms actually represent just one species, whose size varied markedly according to sex and habitat. The largest females in this example of extreme reversed sexual size dimorphism were about 280% the weight and 150% the height of the largest males, which is unprecedented among birds and terrestrial mammals. The combination of molecular and palaeontological data highlights the difficulties of analysing extinct groups, even those with detailed fossil records.
恐鸟（鸟纲；恐鸟目）是大型的重足型植食性鸟类，体重可达250千克（参考文献1），在大约500年前灭绝之前一直主宰着新西兰的生物群落。尽管有丰富的第四纪化石记录，但恐鸟的分类仍然存在问题，目前已确认有11个物种。在新西兰各地发现了三种恐鸟属物种，它们在体型（背部高度1 - 2米）和体重（约34至242千克）上有显著差异。令人惊讶的是，古代线粒体DNA序列显示，这三个物种在每个岛屿内基因上无法区分，但形成了单独的北岛和南岛分支。在这里，我们利用来自一个已灭绝物种的首个性连锁核序列表明，在每个岛屿上，这三种形态实际上只代表一个物种，其大小根据性别和栖息地有显著差异。在这种极端的反向两性体型差异的例子中，最大的雌性体重约为最大雄性的280%，身高约为150%，这在鸟类和陆生哺乳动物中是前所未有的。分子数据和古生物学数据的结合凸显了分析已灭绝类群的困难，即使是那些有详细化石记录的类群。
