Updated phylogenetic scheme based on the complete mitochondrial protein-coding sequence for common parasitic flatworms

Abstract

The entire coding portion of the mitochondrial genome has now been sequenced for 35 species of parasitic flatworms. This has enabled us to prepare an updated phylogenetic scheme for these species using the complete protein-coding sequence. The mitochondrial genome of parasitic flatworms has 12 protein-coding genes (cox1-3; nad1-6; nad4L, atp6 and cob) and nad4L overlaps nad4 by 37 or 40 bp. Nucleotide and translated amino acid sequences were used for phylogenetic analyses, revealing unexpected placements for several species. For example, Opisthorchis felineus is more closely allied with Clonorchis sinensis rather than with its congener, O. viverrini, supporting several published opinions that these taxa belong in a single genus. Intra- and inter-specific pairwise difference comparisons indicate that inter-specific divergence is very slight (less than 10%) between Taenia saginata and T. asiatica, and in the Asian schistosomes. Pairwise differences among the fasciolids is about 25%, but even higher in many cestode and trematode taxa, but does not exceed 40%. Updated mtDNA data for common parasitic flatworms provide rich and valuable sources of genetic markers for species diagnosis/identification, studies in biogeography, phylogeny, genetic variation/ hybridization of genotypes, population genetics and taxonomy/systematics.