| Summary: | 碩士 === 國立中山大學 === 海洋生物研究所 === 89 === Zooxanthellae are very important for the coral reef ecosystem. The diversity of coral hosts is high in the Indo-Pacific, but the diversity of zooxanthellae has not been broadly investigated. Southern Taiwan and Penghu Islands are coral reef and non-reefal communities, respectively. These localities were chosen as the sampling sites for this study to maximize the opportunity of surveying this region in the Indo-Pacific. Zooxanthellae diversity was investigated in 40 host species including 32 species of Scleractinia, 4 species of Actiniaria, 3 species of Milleporina and 1 species of Helioporacea using polymerase chain reaction (PCR) of the ssrRNA gene and restriction fragment length polymorphism (RFLP) patterns. The phylogenetic relationship of partial and complete sequences of the ssrRNA gene were also analysed. Aiptasia puchella harbors clade B; Oulastrea crispata only harbors clade E; while Acropora palifera and Montipora cactus harbor both clades C and E. Zooxanthellae isolated from all except the above 4 host species are identified as "clade C" sensu Rowan and Powers (1991a). Therefore, the clade C is the dominant type in the Indo-Pacific. Phylogenetic analyses based on partial and complete sequences obtained in this study and also from the GenBank data base demonstrate 4 clades (A, B, C and E) in the genus Symbiodinium. Clade E, classed as D3 RFLP type in previous studies, is a distinct clade differing from A, B and C by RFLP and sequencing data. Clade E has only been found in Scleractinia host species collected in shallow-water habitats in the Pacific. The composition of zooxanthellae clades and ecological pattern of polymorphic symbiosis is not consistent with the irradiance adaptation hypothesis in the Caribbean. A literature survey of zooxanthellae in Scleractinian hosts indicates a significant difference between the Caribbean and the Pacific. The documented biogeography of zooxanthellae clades and the ecological pattern of polymorphic symbiosis are also differ between the Caribbean and the Indo-Pacific.
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