We examined the genetic variation and phylogeographic relationships among 10 populations of Lunella granulata from mainland China, Penghu Archipelago, Taiwan Island, and Japan using mitochondrial COI and 16S markers. A total of 45 haplotypes were obtained in 112 specimens, and relatively high levels of haplotype diversity (h = 0.903) and low levels of nucleotide diversity (π = 0.0046) were detected. Four major phylogenetic lineage clusters were revealed and were concordant with their geographic distribution, agreeing with the haplotype network. These results suggested that geographic barrier isolating effects were occurring among the populations. This hypothesis was also supported by a significant genetic differentiation index (FST = 0.709) and by a spatial analysis of molecular variance (SAMOVA) analysis. A mismatch distribution analysis, neutrality tests and Bayesian skyline plots found a single significant population expansion. This expansion occurred on the coast of mainland China before 20–17 ka. Consequently, although the dispersal ability of the planktonic stage and the circulation of ocean currents generally promote genetic exchanges among populations, L. granulata has tended to maintain distinct genetic groups that reflect the respective geographic origins of the constituent lineages. Although the circulation of ocean currents, in principle, may still play a role in determining the genetic composition of populations, long-distance migration between regions is difficult even at the planktonic stage.

a b s t r a c tGenetic variation was surveyed at 11 microsatellite loci and at 517 bp of the mitochondrial control region to investigate the presence of genetic stock structure in swordfish (Xiphias gladius) in four proximal localities of the southwest Indian Ocean. One aim of this study was to serve as a preliminary examination for congruency of structure detected by these two genetic markers, prior to conducting a more comprehensive basin-wide survey of the Indian Ocean and nearby surrounding areas. Analyses of multilocus microsatellite genotypes and mitochondrial control region sequences both revealed a great homogeneity between samples. Genetic diversity detected at the regional scale was not significantly higher than detected at the local scale. Results suggest that the southwest Indian Ocean globally functions as a unique panmictic population. However, some discrete genetic differences appeared that could possibly indicate influence from a second genetic pool in the northern part of the Indian Ocean. This structure appeared to be sex-dependent with genetic differences higher among female than among male samples. This result may indicate a higher level of spawning area fidelity for females with a subsequent sampling bias tending to homogenise male genotypic distributions.

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The phylogenetic relationship of five species belonging to the subfamily Sparinae was investigated using starch‐gel electrophoretic analysis of enzymes in skeletal muscle, heart, eye, liver, and sarcoplasmic protein in skeletal muscle. A total of 38 loci with 105 alleles coding for 25 enzymes and general protein were analysed and scored to calculate the proportion of polymorphic loci at the 95% level (P95), mean heterozygosity over loci (H), average number of alleles per locus (Na), and genetic distance (D). P95 values obtained ranged from 13.16 to 18.42%, H values ranged from 0.042 to 0.057, Na values ranged from 1.21 to 1.42, and an average D value of 0.305 (0.216‐0.386) between congeneric species and 0.801 (0.614‐0.896) between two consubfamilial genera, Acanthopagrus and Sparus, was found. A phenogram constructed on the basis of genetic data was similar to that based on morphometric characters at the genus level. However, discordance does exist among species of Acanthopagrus between the two sets of phenograms constructed. The results of this study support the niche‐width‐variation hypothesis.

Morphometric and genetic data were used to compare two sympatric and morphologically similar species, Acanthopagrus berda and Acanthopagrus taiwanensis, in Dapeng Bay, South-western Taiwan. A principle component analysis of morphological data indicated a distinction between the two species, with pectoral fin length and eye diameter accounting for 32.27% of the variation. Interspecific sequence divergence, based on mtDNA cytochrome b (0.118 +/- 0.01), was larger than intraspecific divergences between haplotypes (0.007 for A. taiwanensis and 0.003 for A. berda). Individuals of the two species clustered into different groups in three phylogenetic trees with 100% bootstrap support. The mean observed heterozygosity for eight microsatellite loci was 0.471 +/- 0.202 for A. taiwanensis and 0.637 +/- 0.145 for A. berda. Nei's unbiased measure of interspecific genetic distance (D(S)) was 1.334. F(ST) (0.134) and R(ST) (0.404) values indicated significant differentiation between species. An unrooted neighbour-joining tree was constructed by allele-sharing distances and the factorial correspondence analysis split all specimens into two distinct clusters. The results of morphometric, mtDNA and microsatellite analyses indicated the presence of two species, A. taiwanensis and A. berda.