Data from: Molecular evidence shows low species diversity of coral-associated hydroids in Acropora corals

A novel symbiosis between scleractinians and hydroids (Zanclea spp.) was recently discovered using taxonomic approaches for hydroid species identification. In this study, we address the question whether this is a species-specific symbiosis or a cosmopolitan association between Zanclea and its coral hosts. Three molecular markers, including mitochondrial 16S and nuclear 28S ribosomal genes, and internal transcribed spacer (ITS), were utilized to examine the existence of Zanclea species from 14 Acropora species and 4 other Acroporidae genera including 142 coral samples collected from reefs in Kenting and the Penghu Islands, Taiwan, Togian Island, Indonesia, and Osprey Reef and Orpheus Island on the Great Barrier Reef, Australia. Molecular phylogenetic analyses of the 16S and 28S genes showed that Acropora-associated Zanclea was monophyletic, but the genus Zanclea was not. Analysis of the ITS, and 16S and 28S genes showed either identical or extremely low genetic diversity (with mean pairwise distances of 0.009 and 0.006 base substitutions per site for the 16S and 28S genes, respectively) among Zanclea spp. collected from diverse Acropora hosts in different geographic locations, suggesting that a cosmopolitan and probably genus-specific association occurs between Zanclea hydroids and their coral hosts.近期，借助水螅虫物种鉴定的分类学手段，研究者发现了石珊瑚类与钟形螅属（Zanclea）水螅虫之间的一种新型共生关系。本研究旨在解答该共生关系究竟属于物种特异性共生，还是钟形螅属与珊瑚宿主之间的泛全球性共生关联。本研究选取线粒体16S核糖体基因、核28S核糖体基因以及内转录间隔区（internal transcribed spacer, ITS）三类分子标记，对采集自中国台湾垦丁与澎湖群岛、印度尼西亚托吉安群岛、澳大利亚大堡礁的鹰礁与奥菲斯岛的142份珊瑚样本展开分析，这些样本涵盖14种轴孔珊瑚属物种以及轴孔珊瑚科的其余4个属。对16S与28S基因的分子系统发育分析结果表明，与轴孔珊瑚共生的钟形螅属物种形成单系群，但钟形螅属整体并非单系群。对ITS、16S及28S基因的分析显示，采集自不同地理区域、不同轴孔珊瑚宿主的钟形螅属物种之间遗传多样性极低甚至完全一致（其中16S与28S基因的平均成对位点碱基替换距离分别为0.009与0.006），这表明钟形螅属水螅虫与珊瑚宿主之间存在泛全球性且大概率属于属特异性的共生关联。