isolation by distance
Springer Online Journal Archives 1860-2000
Abstract Populations of the Calafia pearl oyster Pinctada mazatlanica ofthe American Pacific coasts have been considered endangeredbecause of overfishing and/or alteration to coastal areas. Weassessed genetic variability and the pattern of populationstructure among 9 samples collected from Mexico to Panama, usingmtDNA RFLP analysis of two genes: 12S rRNA and subunit one ofCytochrome oxydase (COI). Haplotype diversity varied from 0.000to 0.856. The Panama population appeared to be monomorphic, whilethe other samples exhibited a level of haplotypic variabilitysimilar to those reported in the literature for the same kind ofanalysis on other bivalves species. A test for the impact ofdemographic history on genetic diversity was applied on thesequence data, and the results were congruent with a recentdecline of population sizes. Genetic differentiation was shown tofollow a scheme of isolation by distance, with low levels ofdifferentiation at the scales of ten to one hundred kilometres,whereas stronger and significant genetic structure was detectedat a larger scale. Three significantly distinct groups could thenbe defined, which correspond to Northern Mexico, Southern Mexico,and Panama.
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