Science2014-06-10 3:04 PM

古DNA揭示不会飞行的鸟类的进化起源 Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution

论文摘要 

平胸类鸟——它们中有些是最大型的不会飞的鸟类——生活在世界上所有的地方;如今,一项新的研究提示它们是通过飞行散布到地球的遥远角落,而不是因为地块分裂迫使它们离散。这项研究说,只是在地块分开之后,这一群体中的大多数成员失去了飞行的能力。
科学家们长期以来认为,平胸类鸟是在冈瓦纳超大陆裂开后演化成为不同物种(从大型的非洲鸵鸟至现在已经灭绝的马达加斯加象鸟到鸡体型大小的新西兰鹬鸵)的。冈瓦纳超大陆包括非洲大陆及马达加斯加,它是漂移的第一个陆块。因此,现有的平胸类鸟物种形成模型提示,非洲鸵鸟与马达加斯加象鸟是平胸类鸟系谱图中最古老的分支。

Kieren J. Mitchell及其同事对2种象鸟的线粒体基因组进行了测序与分析,并将他们导向了一个令人惊讶的结果:这种大型食草类鸟是小体型杂食性鹬鸵的最近支的现存亲缘动物。而鸵鸟只是这些物种的远亲。文章的作者因此说,平胸类鸟物种并非始于一种共同的不会飞的始祖,它们并非受大陆板块分裂的驱动而分开,其演化看来是由会飞的始祖物种的分化所驱动;它们的如象鸟这样的始祖经过长途飞行来到世界的新的角落,在此之后,它们独立地演化成无法飞行的状态。

在其它地方,无法飞行的平胸鸟几乎仅见于缺少掠食性哺乳动物的岛屿上。因此,文章的作者提出,平胸鸟类最初演化成我们今天所见的大型不会飞鸟类的时间可能始于恐龙——这是当时主要的掠食动物——大规模灭绝之后。

Abstract 

The evolution of the ratite birds has been widely attributed to vicariant speciation, driven by the Cretaceous breakup of the supercontinent Gondwana. The early isolation of Africa and Madagascar implies that the ostrich and extinct Madagascan elephant birds (Aepyornithidae) should be the oldest ratite lineages. We sequenced the mitochondrial genomes of two elephant birds and performed phylogenetic analyses, which revealed that these birds are the closest relatives of the New Zealand kiwi and are distant from the basal ratite lineage of ostriches. This unexpected result strongly contradicts continental vicariance and instead supports flighted dispersal in all major ratite lineages. We suggest that convergence toward gigantism and flightlessness was facilitated by early Tertiary expansion into the diurnal herbivory niche after the extinction of the dinosaurs.

Editor's Summary

Ruffling ancient ratite feathers

Biologists have often pointed to the breakup of the supercontinent Gondwana to explain how related species ended up on far-flung continents, but as new research shows, that explanation doesn't fly with ratite birds. Ratite birds are a lineage of large, mostly flightless birds including the African ostrich, the Australian emu, the South American rhea, the diminutive New Zealand kiwi, and the extinct Madagascar elephant bird. Mitchell et al. examined the phylogeny of these birds, adding ancient mitochondrial DNA sequences from the extinct elephant bird. It seems that ratites originated from flighted ancestors who evolved large sizes and loss of flight only after flying to their new homes.

KEYWORDS

SHARE & LIKE

COMMENTS

ABOUT THE AUTHOR

Science

Science Magazine

0 Following 18 Fans 0 Projects 236 Articles

SIMILAR ARTICLES

AbstractThe conservation of sleep across all animal species suggests that sleep serves a vital function. We here report that sleep has a critical funct

Read More

Introduction Recent decades have seen a major international effort to inventory tree communities in the Amazon Basin and Guiana Shield (Amazonia), but

Read More

IntroductionInitiation of protein synthesis is a key step in the control of gene expression. In eukaryotes, initiation is a highly complex process that

Read More

Abstract For decades, social psychological theories have posited that the automatic processes captured by implicit measures have implications for soci

Read More

论文摘要动物界最复杂的眼睛可以在物种口足类甲壳动物(濑尿虾)中找到,其中一些有12种不同类型的光感受器,每种各取样较窄的一组波长,范围包含了深紫外光到远红光(300到720纳米)。在功能上,这种彩色复杂性被视作是谜。当3种或4种色彩通道对色彩辨认来说已经足够时,为何要使用12种色彩通道?对口足类动物行

Read More

论文摘要 首先,在一篇“评论”文章中,Thomas Piketty 和 Emmanuel Saez用“世界顶级收入数据库(WTID)”来比较这两个数值多年来是如何在欧洲和美国演变的;WTID包括了一个世纪之久的有关全球收入的数据以及2个世纪之久的有关个人财富的数据。据研究人员披露,在20世纪之交的时候

Read More

IntroductionCensorship has a long history in China, extending from the efforts of Emperor Qin to burn Confucian texts in the third century BCE to the c

Read More

Many animals, on air, water, or land, navigate in three-dimensional (3D) environments, yet it remains unclear how brain circuits encode the animal's 3D

Read More

Many animals, on air, water, or land, navigate in three-dimensional (3D) environments, yet it remains unclear how brain circuits encode the animal's 3D

Read More

Like mammalian neurons, Caenorhabditis elegans neurons lose axon regeneration ability as they age, but it is not known why. Here, we report that let-7

Read More