海洋科学: 研究開発

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Ribosomal Internal Transcribed Spacer (ITS) DNA Variation in Millepora

Craig S Tepper and Sophia C Gaynor

Two main growth forms of Millepora (fire coral) are present around the islands of The Bahamas: one exhibits a strong, blade-like structure, Millepora complanata, and the other possesses a delicate branch-like structure, Millepora alcicornis. The phylogenetic relationship of these corals has been under considerable debate for over a century due to the existence of a wide-range of intermediate growth forms. Recent genetic analysis using ribosomal DNA (rDNA) suggests the existence of two distinct reproductively isolated cryptic clades that are independent of morphology [1]. However, using repeated rDNA sequences for phylogenetic construction can lead to false phylogenies if repeated sequences have not undergone concerted evolution, a process involving homogenization of individual repeats of a multigene family. We analyzed twenty rDNA clones isolated from a single bladed Millepora colony and found that although variant rDNA sequences were present, rDNA appears to be largely homogenized.