Phylogenetic relationship among some groups of orthopteran based on complete sequences of the mitochondrial COI gene

Complete sequences of the COI gene were used to reconstruct the phylogenetic relationship among 56 species from Orthoptera. We also analyzed the reliability of Orthoptera phylogenetic relationship using translated amino acid sequences of the COI genes. The COI sequences were divided into three data sets on the basis of different codon positions to calculate the Partitioned Bremer support (PBS), and to test the phylogenetic signal in different codon positions of protein-coding genes. The result supports the monophyly of Caelifera and Ensifera; but the monophyly of Acrididae, Catantopidae, Oedipodidae, Arcypteridae and Gomphoceridae are not supported. The P-distances among families vary from 0.107 to 0.153, which are smaller than those of other families, being consist with the classification that these 5 families should be merged into one family (Acrididae). Chrotogonidae and Pyrgomorphidae belong to the superfamily Pyrgomorphoidea. Pamphagidae should be a family alone consistent with Otte’s taxonomic system. According to the PBS values, the 3rd and 1st codon positions contribution more for the Phylogenetic tree branches than the 2nd, and longer sequences contain more informative sites. We further demonstrated that it is feasible for phylogenetic studies at family level to use the genetic distances among COI sequences from different species of Orthopera.