Population genetic structure of Varuna litterata living along the coast of Thailand were examined in this study. The samples were collected from 3 coastal regions: The Andaman sea

Ornate threadfin bream (Nemipterus hexodon) is an economically important fishery species in Southeast Asia. In Thailand, N. hexodon decreased dramatically due to overexploitation for commercial purposes. To construct an effective sustainable management plan, genetic information is necessary. Thus, in our study, the population genetic structure and demographic history of N. hexodon were investigated using 419 bp of the mitochondrial DNA sequence in cytochrome oxidase subunit I gene (mtDNA COI). A total of 142 samples was collected from nine localities in the Gulf of Thailand (Chonburi, Samut Songkhram, Surat Thani, Nakhon Si Thammarat, Songkhla), and the Andaman Sea (Satun, Trang, Krabi, Phang Nga). Fourteen polymorphic sites defined 18 haplotypes, revealing a high haplotype diversity and low nucleotide diversity among nine localities. The Analysis of molecular variance (AMOVA) analysis, pairwise FST, and minimum spanning network result revealed that the genetic structure of N. hexodon was separated into two populations: the Gulf of Thailand and the Andaman Sea population. The genetic structure of N. hexodon can be explained by a disruption of gene flow from the geographic barrier and the Pleistocene isolation of the marine basin hypothesis. Neutrality tests, Bayesian skyline analysis, mismatch distribution, and the estimated values of population growth suggested that N. hexodon had experienced a population expansion. The genetic information would certainly help us gain insight into the population genetic structure of N. hexodon living on the coast of Thailand.

Abstract. Suppapan J, Sangthong P, Songrak A, Supmee V. 2021. Population genetic structure of hard clam (Meretrix lyrata) along the Southern coast of Thailand. Biodiversitas 22: 2489-2496. The hard clam (Meretrix lyrata), which is an economically important fishery item in Southern Thailand, has decreased rapidly due to overexploitation. To construct sustainable management of this species, genetic information is necessary. In our study, the genetic diversity of M. lyrata was investigated based on the variation of the nucleotide sequence (439 bp) of mitochondrial DNA (mtDNA) in the cytochrome oxidase subunit I gene (mtDNA COI). The mtDNA COI sequences of 145 individuals collecting from 6 sampling sites along the Southern coast of Thailand were analyzed. The results revealed that M. lyrata populations showed moderate to low levels of genetic diversity. All of the population genetic structure analysis revealed the genetic differentiation of the hard clam between the Gulf of Thailand and the Andaman Sea populations. Based on these results, a genetic structure of the hard clam M. lyrata in Southern Thailand was possibly caused by a disruptive gene flow from the geographic factors by the Thai-Malay Peninsula. The demographic history test revealed that the hard clam living in Southern Thailand had experienced population expansion. This study provided the first genetic information that could be used for conserving the hard clam M. lyrata in Southern Thailand.

Abstract. Supmee V, Sawusdee A, Sangthong P, Suppapan J. 2020. Population genetic structure of Blue Swimming Crab (Portunus pelagicus) in the Gulf of Thailand. Biodiversitas 21: 4260-4268. The Blue Swimming Crab (Portunus pelagicus) is an important commercial fishery product in the Gulf of Thailand. To provide a strategy for management, information on genetic features is needed. In our study, the population genetic structure and demographic history of the P. pelagicus living in the Gulf of Thailand were analyzed based on the variation of the nucleotide sequence of the mitochondrial DNA in the control region (mtDNA CR). Ninety-seven samples were collected from 5 sampling sites: Rayong, Chonburi, Chumphon, Surat Thani, and Nakhon Si Thammarat provinces in the Gulf of Thailand. Forty-nine haplotypes were identified and 39 private haplotypes were found. An AMOVA showed no genetic structure among populations. The pairwise FST also indicated no statistically significant difference between all possible regional combinations. The topology of a minimum spanning network revealed a star-like topology that was not separated by geographic structure. The historical demographic analysis revealed a stable population size for a long period and followed by a very recent expansion. An absence of a population structure of the P. pelagicus was possibly caused by a high level of gene flow. The results of this study differ from previous studies that used genetic markers in nuclear DNA. Thus, to clear the genetic structure information of P. pelagicus in the Gulf of Thailand, we suggested that more sensitive markers to detect genetic structure should be used in further analysis.