Molecular Phylogeny Of Sisoridae And Species Validity Of Euchiloglanis In China

Molecular phylogenetics has developed very quickly these years. The fundamental principle, research method and analytical flow of molecular phlogenetics, and phylogenetic analysis are briefly reviewed. Also the characteristic and application of multivariate morphometrics, as well as the phylogenetic investigation progress of sisorid fishes, are briefly reviewed too. The above help interpret the significance and methods of the present study.Family Sisoridae was erected by Regan in 1911, which belongs to Siluriformes, Teleostei. There are 20 genra and more than 50 species (among them the genus Glyptothorax includes most of the species of Sisoridae ). Among them, 12 genra are distributed in China. Most of the sisorid fishes are distributed to the mountain region of East Himalayas, in running water and deep valleys. The phylogenetic relationships of the family are not fully identified, and some species validity is still controversial.Liobagrus Kingi and Liobagrus marginatoides were designated as outgroups in the present study. The length of 16S rRNA gene fragment obtained by PCR amplification ranges from 534 to 542 bp in the 11 Sisorid species (31 samples) investigated, and is 532 bp in L . kingi and L . marginatoides. Out of the aligned homologous sequence of 550 sites obtained , the parsimony informative sites are 97 and occupy 17.6%. The evolutionary characteristics of both stems and loops of 16S rRNA gene partial sequence were analyzed. The Kimura's 2-Parameter distances were calculated and molecular phlogenetic trees were reconstructed by using the neighbor-joining (NJ), maximum parsimony (MP), maximum likelihood (ML) methods. The results show that (1) loops are in general more variable than stems , and in loops a strong adenine bias are observed: (2) there does not exist a saturation effect in stems, loops or all positions of the 16S rRNA gene fragments: (3) in the molecular cladogram, Bagarius forms a sister group with Glyptothorax , and Euchiloganis forms a sister group with Pareuchiloglanis, and Exostoma forms a sister group with Glyptosternum: (4) the phlogenetic positions of Pseudecheneis, Exostoma and Glyptosternum are not recognized; the glyptosternoid fishes are not monophyly although they are defined by 13 osteological apomorphies; the incongruence of cladograms between molecular and morphological sets may be caused byless informative sites of the 550 homologous sites; (5) E. Davidi and E. kishinouyei could be the same species according to the genetic distances; P. sinensis and P. anteanalis could be too.The 2nd intron of the S7 ribosomal protein (rpS7) gene is first used to examine the relationships among sisorid fishes. The length of the 2nd intron sequences obtained by PCR amplification ranges from 153 to 168 bp in the 11 Sisorid species (17 samples) investigated, and is 154 bp in Liobagrus kingi and Liobagrus marginatoides. Out of the alignment of 181 nucleotide sites obtained, the parsimony informative sites are 56 and occupy 30.9% of the total sites. Pairwise comparisons of uncorrected sequences distances and Kimura 2-Parameter distances were calculated and molecular phylogenetic trees were reconstructed by using the neighbor-joining (NJ), maximum parsimony (MP), maximum likelihood (ML) methods. Due to the saturation effect, ingroup relationships were analyzed without any outgroup species. Subsequently, the 8. yarrelli was included in phylogenetic anlaysis for rooting the trees. The results indicate that (1) the 2nd intron sequences of the rpS7 gene in sisorid fishes are rich in informative sites and vary remarkably in sequence divergence from 0.6% between close species to 29.9% between distant species: (2) the insertion/deletion of bases occurred frequently in the sequences of the 2nd intron during the evolution of the rpS7 gene, probably the mechanism of which is different from one another-. (3) in the molecular cladogram, Euchiloganis forms a sister group with Pareuchiloglanis, and Pseudecheneis forms a sister group with Glyptostemum-, the phlogenetic positions of Pseudecheneis...