Naked corals: Skeleton loss in Scleractinia
Naked corals: Skeleton loss in Scleractinia
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DOI：
10.1073/pnas.0602444103
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发表时间：
2006-06-13
影响因子：
11.1
通讯作者：
Boore, Jeffrey L.
中科院分区：
文献类型：
--
作者：
Medina, Monica;Collins, Allen G.;Boore, Jeffrey L.
构成现代珊瑚礁框架的石珊瑚根据其外部文石骨架被归类为石珊瑚属（刺胞动物门、珊瑚虫门和六珊瑚门）。然而，统称为“裸珊瑚”假说的持续观念认为石珊瑚骨架并不能定义一个自然群体。三个主要证据表明，一些石珊瑚与一种或多种软体六珊瑚类群的关系比与其他石珊瑚的关系更为密切：（i）形态相似性； (it) 石珊瑚的分子分析缺乏系统发育解析； (iii) 2.4 亿年前 (Ma) 开始的多样化石珊瑚化石记录与至少 300 Ma 的基于分子的起源之间的差异。没有分子证据能够清楚地揭示由石珊瑚谱系和非骨骼化珊瑚虫组成的得到充分支持的进化枝基础上的关系。我们提供了完整的线粒体基因组数据，这些数据提供了强有力的证据，证明石珊瑚的一个分支与 Corallimorpharia 的关系比与另一石珊瑚分支的关系更密切。因此，我们估计起源于 240 至 288 Ma 之间的石珊瑚骨架，很可能在 Corallimorpharia 的祖先中消失了。我们估计 Corallimorpharia 起源于白垩纪晚期至中期的 110 Ma 至 132 Ma 之间，当时正值海洋二氧化碳含量较高，这会影响文石的溶解度。珊瑚类动物因文石骨骼溶解而逃脱了灭绝，但在海洋中人为二氧化碳增加的压力下，一些现代石珊瑚可能没有如此幸运的命运。
Stony corals, which form the framework for modern reefs, are classified as Scleractinia (Cnidaria, Anthozoa, and Hexacorallia) in reference to their external aragonitic skeletons. However, persistent notions, collectively known as the "naked coral" hypothesis, hold that the scleractinian skeleton does not define a natural group. Three main lines of evidence have suggested that some stony corals are more closely related to one or more of the soft-bodied hexacorallian groups than they are to other scleractinians: (i) morphological similarities; (it) lack of phylogenetic resolution in molecular analyses of scleractinians; and (iii) discrepancy between the commencement of a diverse scleractinian fossil record at 240 million years ago (Ma) and a molecule-based origination of at least 300 Ma. No molecular evidence has been able to clearly reveal relationships at the base of a well supported clade composed of scleractinian lineages and the nonskeletonized Corallimorpharia. We present complete mitochondrial genome data that provide strong evidence that one clade of scleractinians is more closely related to Corallimorpharia than it is to a another clade of scleractinians. Thus, the scleractinian skeleton, which we estimate to have originated between 240 and 288 Ma, was likely lost in the ancestry of Corallimorpharia. We estimate that Corallimorpharia originated between 110 and 132 Ma during the late- to mid-Cretaceous, coinciding with high levels of oceanic CO2, which would have impacted aragonite solubility. Corallimorpharians escaped extinction from aragonite skeletal dissolution, but some modern stony corals may not have such fortunate fates under the pressure of increased anthropogenic CO2 in the ocean.