Genetic structure and historical demography of the blue swimming crab (Portunus pelagicus) from southeastern sea of China based on mitochondrial COI gene.

In this study, the population genetic structure and historical demography of the blue swimming crab, Portunus pelagicus, from southeastern sea of China were investigated using cytochrome c oxidase subunit I (COI) gene of mitochondrion. A total of 889 bp segment of COI gene was sequenced, which showed a high haplotype diversity (0.6833-0.8142) and low nucleotide diversity (0.0021-0.0034). Among 30 haplotypes defined in this study, one (H1) was the most dominant (47.7%) and shared by each locality, while the majority (23) were rare and only existed in one individual. The AMOVA analysis revealed a limited population genetic structure, which suggested a high level of gene flow along the distribution areas of China. This conclusion was supported by the pairwise FST comparison values. The topology of the neighbour-joining tree constructed using 30 haplotypes from four localities presented two distinct clades (clade A and clade B). Meanwhile, three sequences of P. pelagicus downloaded from NCBI database showed a high-level divergence with the individuals collected in our study, which might form a new cryptical species. The individuals of clade B were cryptically embedded in the whole population, with a low frequency (7.7-24.2%), while clade A accounted for 75.8-92.3%. Neutrality tests and mismatch analyses suggested a late Pleistocene population expansion for both clade A (47,000-66,000 years ago) and clade B (74,000-100,000 years ago). This study should provide insight into phylogeny, population genetic structure, conservation genetics, and sustainable management of P. pelagicus.

The complete mitochondrial genome of Stolephorus commersonii.

In this study, the complete mitochondrial genome of Stolephorus commersonii is determined. It is 16,734 bp in length and consists of 13 protein-coding genes, 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and a control region. Phylogenetic tree was constructed based on the complete mitogenome of S. commersonii and closely related 17 other species to assess its phylogenic relationship and evolution. The findings of the study will contribute to the phylogenetic classification and the genetic conservation management of S. commersonii.

Genetic diversity and population structure of Portunus sanguinolentus (Herbst, 1783) revealed by mtDNA COI sequences.

In this paper, population genetic diversity and genetic structure of Portunus sanguinolentus distributed along China coast was investigated based on mitochondrial DNA cytochrome c oxidase subunit I (COI) gene. Sixty-eight haplotypes and 71 polymorphic sites were detected in 110 individuals sampled from four localities. The average haplotype diversity (h) and nucleotide diversity (π) were 0.9576 and 0.0051, respectively. Pairwise FST statistics among different localities were negative or low and insignificant, suggesting a widespread gene flow. The AMOVA analysis also indicated a broad genetic exchange among four localities (FST= -0.0039, p = 0.559). The high dispersal capabilities of larvae of P. sanguinolentus coupled with the limited physical barriers in marine environment may be responsible for the high gene flow among P. sanguinolentus populations along southeastern coast of China. Moreover, neutrality test and mismatch analysis implied that P. sanguinolentus population might have undergone a rapid population expansion event. The time of population expansion was estimated to occur about 229,000-321,000 years ago.

Pronounced population genetic differentiation in the rock bream Oplegnathus fasciatus inferred from mitochondrial DNA sequences.

The population genetic structure of the rock bream (Oplegnathus fasciatus) along the coastal waters of China was estimated based on three mtDNA fragments (D-loop, COI, and Cytb). A total of 112 polymorphic sites were checked, which defined 63 haplotypes. A pattern with high levels of haplotype diversity (hCOI = 0.886 ± 0.034, hCytb = 0.874 ± 0.023) and low levels of nucleotide diversity (лCOI = 0.009 ± 0.005, лCytb = 0.006 ± 0.003) was detected based on the COI and Cytb fragments, and high levels of genetic diversity (hD-loop = 0.995 ± 0.007, лD-loop = 0.021 ± 0.011) were detected from the mtDNA D-loop. The population genetic diversity of O. fasciatus in south China was significantly higher than those of north China. Three genealogical clades were checked in the O. fasciatus populations based on the NJ and MST analyses of mtDNA COI gene sequence, and the genetic distances among the clades ranged from 0.018 to 0.025. Significant population genetic differentiation was also checked based on the Fst (0.331, p = 0.000) and exact p (0.000) test analyses. No significant population differentiations were checked based on mtDNA D-loop and Cytb fragments. Using a variety of phylogenetic methods, coalescent reasoning, and molecular dating interpreted in conjunction with paleoclimatic and physiographic evidences, we inferred that the genetic make-up of extant populations of O. fasciatus was shaped by Pleistocene environmental impacts on the historical demography of this species. Coalescent analyses (neutrality tests, mismatch distribution analysis, and Bayesian skyline analyses) showed that the species along coastline of China has experienced population expansions originated in its most recent history at about 169-175 kya before present.

Genetic diversity and population structure of largehead hairtail, Trichiurus japonicus, based on mtDNA control region.

Largehead hairtail, Trichiurus japonicus, is a valuable commercially exploited demersal species. We gathered mtDNA control region sequences (3' mtDNA CR) of T. japonicus to investigate its genetic diversity and population genetic structure. Fifty-four specimens were collected from the nearshore localities along the coastline of China. A total of 42 polymorphic sites were found, which defined 40 haplotypes. A pattern with high level of haplotype diversity (h = 0.98 ± 0.01) and very low level of nucleotide diversity (π = 0.008 ± 0.005) were detected in the examined range. Comparing π with other fish species shows that T. japonicus has remarkable low genetic diversity values compared with other Pacific Ocean marine fishes. AMOVA and conventional Fst values revealed no significant genetic structure throughout the examined range, which is inconsistent with the previous findings based on the morphological and ecological studies. Using a variety of phylogenetic methods, coalescent reasoning, and molecular dating interpreted in conjunction with paleoclimateic and physiographic evidence, we infer that the genetic make-up of extant populations of T. japonicus was shaped by Pleistocene environmental impacts on the historical demography of this species. Coalescent analyses (Neutrality tests, Mismatch distribution analysis, Bayesian skyline analyses) showed that the species along the coastline of China has experienced population expansions originated in its most recent history at about 153-216 kyr.

The complete mitochondrial genome sequence of Schizopygopsis younghusbandi (Cypriniformes: Cyprinidae).

In this paper, we determined complete mitochondrial DNA sequence of Schizopygopsis younghusbandi. The mitogenome is 16,674 bp in length, which includes 22 tRNA genes, 2 rRNA genes, 13 protein-coding genes, and 2 non-coding regions: control region (D-loop) and origin of light-strand replication (OL). The complete mitogenome sequence of S. younghusbandi is useful to the studies on taxonomic status, molecular systematics, stock evaluation, and conservation genetics.

The complete mitochondrial genome sequence of Schizothorax wangchiachii (Cypriniformes: Cyprinidae).

In this study, the complete mitochondrial DNA (mtDNA) sequence of Schizothorax wangchiachii has been determined. The mitogenome is 16,593 bp in length. It consists of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and 2 non-coding regions: origin of light-strand replication (OL) and control region (D-loop). The complete mtDNA sequence of S. wangchiachii can contribute to elucidate the evolutionary mechanisms and biogeography of Schizothorax and is useful to stock evaluation and conservation genetics for S. wangchiachii.