Chippindale Paul T, Bonett Ronald M, Baldwin Andrew S, Wiens John J
Department of Biology, University of Texas at Arlington, Arlington, Texas 76019, USA.
Evolution. 2004 Dec;58(12):2809-22. doi: 10.1111/j.0014-3820.2004.tb01632.x.
The transition from aquatic to terrestrial eggs is a key evolutionary change that has allowed vertebrates to successfully colonize and exploit the land. Although most amphibians retain the primitive biphasic life cycle (eggs deposited in water that hatch into free-living aquatic larvae), direct development of terrestrial eggs has evolved repeatedly and may have been critical to the evolutionary success of several amphibian groups. We provide the first conclusive evidence for evolutionary reversal of direct development in vertebrates. The family Plethodontidae (lungless salamanders) contains the majority of salamander species, including major radiations of direct developers. We reconstruct the higher level phylogenetic relationships of plethodontid salamanders using molecular and morphological data and use this phylogeny to examine the evolution of direct development. We show that the predominantly biphasic desmognathines, previously considered the sister group of other plethodontids, are nested inside a group of direct-developing species (Plethodontini) and have re-evolved the aquatic larval stage. Rather than being an evolutionary dead end, the reversal from direct developing to biphasic life history may have helped communities in eastern North America to achieve the highest local diversity of salamander species in the world.
从水生卵到陆生卵的转变是一项关键的进化变革，它使脊椎动物得以成功地在陆地上开拓并利用陆地环境。尽管大多数两栖动物保留着原始的双相生命周期（卵产在水中，孵化出自由生活的水生幼体），但陆生卵的直接发育已经多次进化，并且可能对几个两栖动物类群的进化成功起到了关键作用。我们提供了脊椎动物直接发育进化逆转的首个确凿证据。无肺螈科（无肺蝾螈）包含了大多数蝾螈物种，包括直接发育者的主要辐射类群。我们利用分子和形态学数据重建了无肺螈科蝾螈的高级系统发育关系，并利用这个系统发育关系来研究直接发育的进化。我们表明，以前被认为是其他无肺螈科姐妹群的主要双相的脊口螈属，嵌套在一组直接发育的物种（无肺螈属）之中，并且已经重新进化出了水生幼体阶段。从直接发育到双相生活史的逆转并非进化的死胡同，它可能帮助北美东部的群落实现了世界上蝾螈物种最高的局部多样性。
