珊瑚在不同環境中的生殖變異及存活率

Considering the rapid rate of mortality in coral reef species around the globe, there is an urgent need to fill literature gaps concerning baseline information, specifically related to coral life history traits and their mechanisms to respond to local environmental changes. This research would allow for higher success in conservation and restoration actions. This PhD dissertation aims first to contribute to our understanding on the natural variations in the reproductive biology of reef-building corals living under different environmental conditions. The comparative analyses in the reproductive and genetic traits of the hermaphroditic broadcast spawning coral Acropora hyacinthus across six different latitudes [Japan (33° and 31°N), Taiwan (23°, 22° and 21°N), and Indonesia (5°S)], in the Western Pacific Region, indicated natural variability in its reproductive traits, as well as reproductive trade-offs across locations. These results were not confounded by genetics as there was evidence of active gene flow among low-, mid- and high-latitude locations, with the exception of one location in the West of Taiwan suggesting reproductive isolation with local adaptations. Further analysis of the natural spatial and temporal variability in the reproductive traits of A. hyacinthus from tropical and temperate locations, indicated significant spatial differences only in egg sizes, while a significant temporal difference in both fecundity (i.e. egg number) and egg volume is only reported at the temperate location. Contrary, male gonad values varied significantly among years at both locations. Spatial and temporal differences in the reproductive trade-offs are reported. These results may serve as baseline information in the evolutionary strategies and reproductive trade-offs that A. hyacinthus may use in order to maximize its annual reproductive efforts at tropical and temperate locations. Experimental procedures aimed at investigating the phenotypic plasticity of reef-building corals were developed using reciprocal transplantations of four widely dispersed coral species, Favites pentagona, Acropora gemmifera, Acropora hyacinthus and Stylophora pistillata, all naturally occurring in the south (tropical) and north (sub-tropical) of Taiwan Island. There was faster and higher mortality of sub-colonies (i.e. genets) moved from the tropical to the sub-tropical location. Sub-colonies from the sub-tropical location moved to the tropical location, although remaining alive during the initial months, all bleached and died after the summer months (one year after transplantations). These results (that may or may not be related to climatic factors) suggest limited adaptations capacities and high sensitivity of these corals to conditions outside their historic ranges such as very low or high sea water temperatures, different local predators and/or symbiotic compositions, among others. Finally, considering that all DNA sequences as well as measurements of reproductive traits of A. hyacinthus from all locations studied have been submitted to freely available online databases, and with the intension to bridge the scientific knowledge into active conservation practices, an user friendly decision-support web tool is introduced (www.coralreefrestoration.com), aiming to assist anyone interested in developing coral restoration projects throughout the world.

並列關鍵字

Phenotypic plasticity ； Coral reproduction ； Latitudinal comparison ； Genetics

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國際替代計量

珊瑚在不同環境中的生殖變異及存活率

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