Evolutionary characteristics of the fish mitochondrial DNA and its utilization for analysis of population and phylogeny

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Though the mitochondrial DNA (mtDNA) has been utilized for population and phylogeny analysis of fishes as a primary source of genetic markers, its evolutionary characteristics have not been clarified enough. In this project, evolutionary characteristics of the mtDNA were examined through analyzing the two ribosomal RNA genes, several protein-coding genes, and the control region. In addition, by using sequence data from these genes, population structure analysis and phylogenetic analysis of closely related species as well as distantly related species of fishes were made. Main points of the results are as follows. 1) The control region is useful for population and phylogeny analysis of intraspecific populations or closely related species because of its high variability, but there are some .exceptions that this region is not so variable. 2) Phylogenetic information from the ribosomal RNA genes is sometimes not enough for resolving phylogenetic relationships among distantly related groups such as families. 3) For analysis of deep-branches, compilation of data from many protein-coding genes appears to be useful. 4) A "molecular clock" from a couple of protein-coding genes was calibrated for fishes. During this study, an effective method for amplifying and sequencing of a total mitochondrial genome of fishes was established by utilizing so-called the long PCR techniques. In the next step of this study, the new method can be fully utilized in obtaining and characterizing complete mtDNA sequences from many fishes, and the resulting sequence data will be effectively used for examining phylogenetic relationships of major groups of fishes in detail.