Cyclestheria hislopi (Crustacea: Branchiopoda): a group of morphologically cryptic species with origins in the Cretaceous.
Cyclestheria hislopi (Crustacea: Branchiopoda): a group of morphologically cryptic species with origins in the Cretaceous.
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DOI：
10.1016/j.ympev.2012.11.005
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发表时间：
2013-03
影响因子：
4.1
通讯作者：
Martin Schwentner;S. Clavier;M. Fritsch;J. Olesen;Sameer M. Padhye;B. Timms;S. Richter
中科院分区：
文献类型：
--
作者：
Martin Schwentner;S. Clavier;M. Fritsch;J. Olesen;Sameer M. Padhye;B. Timms;S. Richter
环兽目（Cyclestheria hislopi）被认为是环兽目中唯一现存的物种。它是所有枝角类的姐妹分类群，并显示出刺尾类和枝角类的中间形态特征。利用一个线粒体标记（COI）和两个核标记（EF 1 α和28 SrRNA），我们验证了C. hislopi代表一个单一的环热带物种。南美洲（法属圭亚那），亚洲（印度，印度尼西亚，新加坡）和几个澳大利亚人口包括在我们的调查。系统发育分析和遗传距离分析表明，两个品种存在显著的洲际遗传分化（未校正p距离COI> 13%，EF 1 α>3%，28 S>4%）。每个大陆都发现至少有一个不同的环兽属物种，澳大利亚拥有四个不同的主要谱系，可能归因于两到三个物种。根据COI和EF 1 α的系统发育分析，结合使用几个化石腕足类校准点或COI每百万年1.4%的替代率的分子钟估计，这些物种（构成冠群环兽目）的分歧可以追溯到白垩纪。这是南美血统从亚洲-澳大利亚血统中分裂出来的时候，后者在古近纪进一步分化。今天的环热带分布的Cyclestheria可能是最好的解释冈瓦纳的vicariance和后来的分散在亚洲和澳大利亚的组合时，两个大陆的构造板块在中新世早期拉近。缺乏形态分化，已经发生在这个分类群在这样一个漫长的进化时期与高水平的分化和多样化观察到它的姐妹分类群枝角类。对环兽目进化的进一步了解可能有助于我们理解枝角类的进化成功。
Cyclestheria hislopi is thought to be the only extant species of Cyclestherida. It is the sister taxon of all Cladocera and displays morphological characteristics intermediate of Spinicaudata and Cladocera. Using one mitochondrial (COI) and two nuclear (EF1α and 28S rRNA) markers, we tested the hypothesis that C. hislopi represents a single circumtropic species. South American (French Guiana), Asian (India, Indonesia, Singapore) and several Australian populations were included in our investigation. Phylogenetic and genetic distance analyses revealed remarkable intercontinental genetic differentiation (uncorrected p-distances COI>13%, EF1α>3% and 28S>4%). Each continent was found to have at least one distinct Cyclestheria species, with Australia boasting four distinct main lineages which may be attributed to two to three species. The divergence of these species (constituting crown group Cyclestherida) was, on the basis of phylogenetic analyses of COI and EF1α combined with molecular clock estimates using several fossil branchiopod calibration points or a COI substitution rate of 1.4% per million years, dated to the Cretaceous. This was when the South American lineage split from the Asian–Australian lineage, with the latter diverging further in the Paleogene. Today’s circumtropic distribution of Cyclestheria may be best explained by a combination of Gondwana vicariance and later dispersal across Asia and Australia when the tectonic plates of the two continents drew closer in the early Miocene. The lack of morphological differentiation that has taken place in this taxon over such a long evolutionary period contrasts with the high level of differentiation and diversification observed in its sister taxon the Cladocera. Further insights into the evolution of Cyclestheria may help us to understand the evolutionary success of the Cladocera.