Reimer James Davis, Takishita Kiyotaka, Ono Shusuke, Tsukahara Junzo, Maruyama Tadashi
Research Program for Marine Biology and Ecology, Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan.
Zoolog Sci. 2007 Apr;24(4):346-59. doi: 10.2108/zsj.24.346.
Interspecific hybridization has been proposed as a possible explanation for the incredible diversity seen in reef-dwelling corals, but until now little proof of such hybridization in other reef-dwelling anthozoans has been reported. Without further observation of hybridization, the question of such a phenomenon being widespread in Anthozoa remains. Here we have examined the mitochondrial cytochrome oxidase I gene (COI) and the nuclear internal transcribed spacer of ribosomal DNA (ITS-rDNA) from three species of the mass-spawning, encrusting anemone genus Zoanthus (Z. sansibaricus, Z. kuroshio, Z. gigantus) to investigate possible hybridization. The three species coexist at two of three sampling locations in southern Japan. Zoanthus spp. ITS-rDNA region spacers (ITS-1 and ITS-2) were shown to have very high rates of divergence. At locations where all three species co-existed, several of our sampled Z. sansibaricus individuals (with identical "sansi" COI sequences) possessed two very divergent (i.e., species-level difference) ITS-rDNA alleles, the expected "sansi" allele and the divergent "B" allele. Additionally, two Z. sansibaricus individuals possessed only "B" alleles despite having "sansi" COI sequences. These results indicate that Z. sansibaricus has possibly experienced interspecific hybridization at least once with a Zoanthus partner possessing the "B" allele, and that these resulting hybrids may also sexually reproduce, demonstrating potential hybridization occurring in the order Zoantharia (Hexacorallia).
种间杂交被认为是珊瑚礁栖息珊瑚呈现出惊人多样性的一种可能解释，但直到现在，关于其他珊瑚礁栖息的珊瑚虫纲动物存在这种杂交的证据报道很少。在没有对杂交进行进一步观察的情况下，珊瑚虫纲中这种现象是否普遍存在的问题依然存在。在这里，我们检测了三种大量产卵、具壳的海葵属动物（桑给巴尔海葵、黑潮海葵、巨大海葵）的线粒体细胞色素氧化酶I基因（COI）和核糖体DNA的核内转录间隔区（ITS-rDNA），以研究可能的杂交情况。这三个物种在日本南部三个采样地点中的两个地点共存。海葵属动物的ITS-rDNA区域间隔序列（ITS-1和ITS-2）显示出非常高的分歧率。在所有三个物种共存的地点，我们采样的一些桑给巴尔海葵个体（具有相同的“桑西”COI序列）拥有两个差异极大的（即物种水平差异）ITS-rDNA等位基因，预期的“桑西”等位基因和差异较大的“B”等位基因。此外，两个桑给巴尔海葵个体尽管具有“桑西”COI序列，但仅拥有“B”等位基因。这些结果表明，桑给巴尔海葵可能至少与拥有“B”等位基因的海葵属伙伴进行过一次种间杂交，并且这些产生的杂交后代也可能进行有性繁殖，这表明在六放珊瑚亚纲的群体海葵目中可能发生了杂交。
