木珊瑚科Cladopsammia gracilis和Rhizopsammia wettsteini线粒体全基因组比较与系统进化分析

Complete mitochondrial genome of Cladopsammia gracilis and Rhizopsammia wettsteini(Scleractinia,Dendrophylliidae)and its phylogenetic implications

木珊瑚科(Dendrophylliidae)下的枝沙珊瑚属(Cladopsammia)和Rhizopsammia属的物种分类目前仍存在模糊的界定,本研究结合形态特征与微观结构和线粒体全基因组测序对Cladopsammia gracilis与Rhizopsammia wettsteini进行形态和分子进化水平的分析比较。结果显示:形态学特征上,R.wettsteini通过生殖根出芽,珊瑚肋上具有小尖状突起,隔片薄而脆;而C.gracilis则无生殖根,珊瑚肋上突起为细瘤状,隔片颗粒感强且较厚。两个物种的线粒体基因组组成十分相似,同样包含13个蛋白编码基因、2个rRNA基因和2个tRNA基因,与大部分六放珊瑚相同;在基因重叠情况和密码子偏好性上则有别于大部分六放珊瑚。基于CO1基因的系统进化分析显示,C.gracilis和R.wettsteini关系较近,却与枝沙珊瑚属(Cladopsammia)其他物种关系较远,因此C.gracilis是否归入枝沙珊瑚属(Cladopsammia)值得探讨,同时提示我们需要重新审视枝沙珊瑚属(Cladopsammia)的分类地位。

There is a taxonomic uncertainty on the species classification of Cladopsammia gracilis and Rhizopsammia wettsteini well as the unresolved status of the closely related genera Cladopsammia and Rhizopsammia.In order to further analyze the phylogenetic relationship between C.gracilis and R.wettsteini,we examined the micromorphological and microstructural features and systematically compared the gene structure,genetic distance and codon preference of two mitochondrial genomes.The results show that there are three distinct characteristics:reptoid budding,costae and septa.The genome composition of the two species is very similar,containing 13 protein-coding genes,2 rRNA genes and 2 tRNA genes.Unlike most scleractinians,there were no overlaps between genes.In addition,phylogenetic analysis based on CO1 genes show that C.gracilis and R.wettsteini are closely related but distantly related to other species of the genera Cladopsammia.The present study highlights the need for an integrative approach to conduct a deeper species delimitation of genera Cladopsammia and Rhizopsammia.