title: Genetic variations in two seahorse species (Hippocampus mohnikei and Hippocampus trimaculatus): evidence for middle Pleistocene population expansion.
abstract: Population genetic of seahorses is confidently influenced by their species-specific ecological requirements and life-history traits. In the present study, partial sequences of mitochondrial cytochrome b (cytb) and control region (CR) were obtained from 50 Hippocampus mohnikei and 92 H. trimaculatus from four zoogeographical zones. A total of 780 base pairs of cytb gene were sequenced to characterize mitochondrial DNA (mtDNA) diversity. The mtDNA marker revealed high haplotype diversity, low nucleotide diversity, and a lack of population structure across both populations of H. mohnikei and H. trimaculatus. A neighbour-joining (NJ) tree of cytb gene sequences showed that H. mohnikei haplotypes formed one cluster. A maximum likelihood (ML) tree of cytb gene sequences showed that H. trimaculatus belonged to one lineage. The star-like pattern median-joining network of cytb and CR markers indicated a previous demographic expansion of H. mohnikei and H. trimaculatus. The cytb and CR data sets exhibited a unimodal mismatch distribution, which may have resulted from population expansion. Mismatch analysis suggested that the expansion was initiated about 276,000 years ago for H. mohnikei and about 230,000 years ago for H. trimaculatus during the middle Pleistocene period. This study indicates a possible signature of genetic variation and population expansion in two seahorses under complex marine environments.
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Vero Beach Marine Laboratory, Florida Institute of Technology, Vero Beach, Florida, United States of America.
authors.forename: Nancy Kim
authors.initials: NK
authors.lastname: Pham
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Huixian
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Vero Beach Marine Laboratory, Florida Institute of Technology, Vero Beach, Florida, United States of America.
authors.forename: Junda
authors.initials: J
authors.lastname: Lin
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Lin
mesh_terms: D000818:Animals; D002681:China; D045303:Cytochromes b / Q000235:genetics; D004272:DNA, Mitochondrial; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D006239:Haplotypes; D008969:Molecular Sequence Data; D010802:Phylogeny; D011157:Population Dynamics; D017422:Sequence Analysis, DNA; D023701:Smegmamorpha / Q000145:classification / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D045303:Cytochromes b