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POPULATION GENETIC STRUCTURE AND EXPANSION ANALYSIS OF GREEN MUD CRAB (SCYLLA PARAMAMOSAIN) FROM BEIBU GULF

Mitochondrial 16S rRNA gene fragment was employed to analyze population genetic structure and expansion history of green mud crab (Scylla paramamosain) from Beibu gulf. The 16S rRNA gene fragments ranged from 521 to 523bp in length and 21 haplotypes were defined in six geographic stocks of green mud crab. Total haplotype diversity (h) and nucleotide diversity (π) were 0.6259 and 0.001851, respectively. No correlation was detected between genetic dis- tances and geographic distances. Genetic differentiation coefficients (G st ) of pairwise populations extended from 0.02008 to 0.04362, while gene flows (N m ) from 5.48 to 12.20. An analysis of molecular variance (AMOVA) showed that variance within populations accounted for 0.1%, while among populations accounted for 99.9%. The absolute values of fixation indices in the scope of 0.00026—0.02977 suggested no genetic differentiation for pairwise populations. Neighbour-joining tree and median-joining network generated from haplotype data set displayed no apparent lineage clades association with sampling locations. Neutral test and mismatch-distribution analysis disclosed that the populations of green mud crab from Beibu gulf had ever experienced population expansion, whose expansion time was roughly estimated at the late Pleistocene (0.04698—0.01879MY ago or 0.04520—0.01808MY ago).