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National Committee on Marine Sciences (NCMS)

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1986 - 198911990 - 19921

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Author: search.filters.author.Macaranas, J. M.SDG: search.filters.sdg.SDG 14 - Life below water

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    Genetic structure of giant clam (Tridacna derasa) populations from reefs in the Indo-Pacific
    Macaranas, J. M.; Ablan, C. A.; Pante, M. J. R.; Benzie, J. A. H.; Williams, S. T. (Springer, 1992-06)
    Large genetic differences were observed among the Great Barrier Reef (GBR), Fiji and Philippine populations of Tridacna derasa (Roding) sampled in 1989 and 1990 (Nei's unbiased genetic distance, D,=0.137 to 0.341). This result contrasted strongly with the low genetic distance (D=0.032) reported previously for the giant clam T. maxima over similar geographical scales. No significant genetic differentiation was observed among most populations from the GBR (mean D=0.007), consistent with the high gene exchange expected in this highly connected reef system. However, significant differentiation resulting from differences in the frequencies of less common alleles between the North-Central GBR and South GBR (Swain region) were observed. Historical isolation of blocks of the Central Indo-West Pacific from the GBR and present-day restrictions to gene exchange between the GBR, Fiji and the Philippines as a result of oceanographic current patterns, were thought to be responsible for the high degree of genetic differentiation of T. derasa populations. The relevance of these findings to clam mariculture and reef restocking are briefly discussed.
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    Electrophoretic evidence for extensive hybrid gene introgression into commercial Oreochromis niloticus (L.) stocks in the Philippines
    Macaranas, J. M.; Taniguchi, N.; Pante, M. J. R.; Capili, J. B.; Pullin, R. S. V. (Hindawi Limited, 1986-10)
    The usefulness of isozyme and protein markers in identifying tilapia species and their hybrids is demonstrated. Genetic characterization of Oreochromis niloticus populations from commercial farms, experimental stations, and government hatcheries in Luzon, Visayas and Mindanao in the Philippines indicates well-established introgression with O. mossambicus. Genetic differentiation of the O. niloticus stocks, measured by Nei's genetic distance, was highly correlated with O. mossambicus gene content. The implications of these results for tilapia genetic improvement are discussed.