Comparative Phylogeography and Phylogeny of Pennah Croakers (Teleostei: Sciaenidae) in Southeast Asian Waters.

A broad-scale comparative phylogeographic and phylogenetic study of pennah croakers, mainly Pennahia anea, P. macrocephalus, and P. ovata was conducted to elucidate the mechanisms that may have driven the diversification of marine organisms in Southeast Asian waters. A total of 316 individuals from the three species, and an additional eight and six individuals of P. argentata and P. pawak were employed in this study. Two genetically divergent lineages each of P. argentata and P. anea (lineages L1 and L2) were respectively detected from the analyses based on mitochondrial cytochrome b gene data. Historical biogeography analysis with a multi-gene dataset revealed that Pennahia species most likely originated in the South China Sea and expanded into the eastern Indian Ocean, East China Sea, and northwestern Pacific Ocean through three separate range expansions. The main diversifications of Pennahia species occurred during Miocene and Pliocene periods, and the occurrences of lineage divergences within P. anea and P. argentata were during the Pleistocene, likely as a consequence of cyclical glaciations. The population expansions that occurred after the sea level rise might be the reason for the population homogeneity observed in P. macrocephalus and most P. anea L2 South China Sea populations. The structure observed between the two populations of P. ovata, and the restricted distributions of P. anea lineage L1 and P. ovata in the eastern Indian Ocean, might have been hampered by the northward flowing ocean current at the Malacca Strait and by the distribution of coral reefs or rocky bottoms. While our results support S. Ekman's center-of-origin hypothesis taking place in the South China Sea, the Malacca Strait serving as the center of overlap is a supplementary postulation for explaining the present-day high diversity of pennah croakers centered in these waters.

Cytochrome b gene reveals panmixia among Japanese Threadfin Bream, Nemipterus japonicus (Bloch, 1791) populations along the coasts of Peninsular Malaysia and provides evidence of a cryptic species.

We evaluated genetic differentiation among ten presumed Japanese threadfin bream, Nemipterus japonicus populations along the coast of Peninsular Malaysia based on the partial sequence of the mitochondrial cytochrome b gene (982 bp). Genetic divergences (Kimura-2 parameter) ranged from 0.5% to 0.8% among nine of the ten populations while these nine populations were 4.4% to 4.6% diverged from the Kuala Besar population located at the Northeast coast. The constructed Neighbour Joining (NJ) phylogenetic trees based on haplotypes showed the Kuala Besar population forming an isolated cluster. The Analysis of Molecular Variance (AMOVA) of the ten populations a priori assigned into four regions, revealed that most of the variation occurred within population with a fairly low but significant level of regional differentiation (FST = 0.07, p < 0.05, FSC = 0.00, p > 0.05 and FCT = 0.07, p < 0.05) attributed to the Kuala Besar population. p Value after Bonferroni correction revealed that only pairwise FST values involving the Kuala Besar population with the other nine populations were significant. Thus, this study revealed that the N. japonicus populations off Peninsular Malaysia were panmictic. However, the Kuala Besar population, although morphologically identical was composed of a genetically discrete taxon from the rest. These findings are important contributions in formulating sustainable fishery management policies for this important fishery in Peninsular Malaysia.