Sequences and Phylogeny of Partial Mitochondrial COⅠ Gene from Four Brachionus Species

The partial mitochondrial COⅠ gene was sequenced from 40 individuals of four Brachionus species.The sequences were compared and their molecular phylogenetic trees were constructed by UPGMA,neighbor-joining and maximum parsimony methods using B.plicatilis as outgroup.The length of sequences was 543 bp,in which frequency of A+T was 65.3%,and a considerable variation of 157 nucleotide sites (28.9%) was detected.All of three trees suggested that B.quadridentatus is relatively closer to B.urceus than other species,and then to B.leydigi,last to B.calyciflorus.This result is consistent with that of traditional morphological taxonomy.