Study On Phylogenetic Of Notothenioidei And Genetic Diversity Of Trematomus Bernacchii Populations

The Notothenioidei is the most species order of the Antarctic notothenioids,the dominant taxonomic component of Antarctic's Osteichthyes,belonging to the Perciformes,just as the good material for this research,and long times ago the benthic fishes where lives in the temperate developed and evolution the Notothenioidei.Trematomus bernacchii,belonging to the Perciformes,Notothenioidei,Nototheniidae,is a species widely distributed in the Antarctic for adapt the cold environment,although it has smaller body,limited number,but because it has important scientific significance and the economic value in radiation research of cold adaptation and adaptive mechanism of concern for the world.The mitochondrial cytochrome b gene and cytochrome oxidase gene combined to the analysis of the 5 groups(Great Wall Station CCZ,Ross Sea LSH,Casey Station KXZ,Davies station DWSZ,Zhongshan Station ZZZ)to investigate the diversity,population structure,population genetic and evolutionary history,in order to provide basis for the effective management of T.bernacchii's and reasonable exploitation to utilization of data support;as the same time we identified the Notothenioidei to amplification the COI sequences for research the relationship of Channichthyidae and Nototheniinae.The main contents are as follows:1.Study on genetic diversity and population history of T.bernacchii:Cytb and COI analysisChoosing the general PCR technology for the amplification of mitochondrial COI and Cytb gene of five groups of T.bernacchii(Great Wall Station,Ross Sea,Casey Station,Davies station,Zhongshan Station).A total of 98 specimens from five sampling sites were collected and analyzed to find 42 different haplotypes.In most cases,the haplotype diversity(H_=0.866?0.030)level was high,while the nucleotide diversity was relatively low(Pi=0.00253?0.00054).The base content of A+T(53%)is higher than G+C(47%).The average intra-specific genetic distance is 0.3%,the distance between each sampling sites ranges respectively found to be 0.1733%-0.714%.The results of AMOVA analysis showed that the variation among the groups was 4.65%(P<0.05)and 95.35%(P<0.05)in the group.With the cluster analysis method to build phylogenetic trees and determinethe evolutionary relationship between the sequences.The results indicate that the groups of T.bernacchii does not have a distinct geographical.Neutral evolutionary analysis showed that the groups of T.bernacchii experienced a period of rapid expansion about one million years ago(about the Pleistocene).Both molecular variance analysis and Fst analysis showed that the genetic variation of T.bernacchii mainly came from individuals in the specimens,and few came from the populations.The results show that there are certain genetic exchange among five sampling points in the Antarctic,which is a random mating group.2.Analysis of the structrue of Notothenioidei based on COI sequencesThe Southern Ocean area accounts 10%of the world's ocean area but has low species richness,because of some areas was subject to commercial fishing,we were not well known the fauna and suspected species was underestimated.As a promising tool,DNA barcoding has been advanced to acid species identification and discovery.Even for experts,in spite of extensive taxonomic studies,the identification of fishes can be problematic for a variety of reasons,and the phylogenetic relationship between species.Here,25 Antarctic fish species was discrimination efficiency of barcoding,and examine the utility of these data.We collected and morphologically identified specimens during Southern Ocean collected 2013 and 2016.In total,58 single individuals of 23 species pertaining to 16 genera of Notothenioidei and Channichthyidae was barcoded by COI gene,sequenced and compared with that of other species recorded in GenBank and the Barcode of Life Data System(BOLD).Our results indicate that the mean T,G,A,and C contents were 31.9%,18.1%,22%,and 28%,the GC content of codon position 1 averaged 45.1%,that of position 2 in average of 50.7%,and that of position 3 for 42.3%.respectively the COI sequence of Antarctic fisheswereobviouslybasebiased.Theaveragevalueof transition/transversion ratios was 3.47.By using Kimera-2-parameter model to calculated,the mean genetic distance among pairwise-species(0.0447)was 17 times as big as that within-species(0.0027).From the phylogenetic tree,the 25 species,except for Cryodraco antarcticus and Cryodraco atkinsoni could cluster respectively,which suggested that COI barcoding could effectively to identify the remaining 25 species.Through this study compared with other studies,we found that differences methods and sampling can lead to differences result.To have better research the phylogenetic relationship of fish,we need to analyze a variety of methods together to form a more consistent system tree.In the course of the study,we found that for some sister species or recently differentiated subspecies,COI barcoding mostly cannot be separated,hoping to use mitochondrial genes and nuclear genes together to analyze.