Submitted to: Molecular Biology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 2000
Publication Date: November 17, 2000
Interpretive Summary: Mitochondrial (mt) genomes have been used in numerous studies to investigate phylogenetic relationships among eukaryotes at many levels. In recent years, the arrangement of genes in the mt genome has been regarded as a powerful record of historical relationships where changes in mt gene order occur infrequently even over considerable spans of time. Herein, our research focussed on investigating the reliability of gene order to infer phylogenetic relationships. Mitochondrial gene orders from a host of nematodes and trematodes were determined by DNA sequence analysis and subsequently compared. Striking results were identified indicating that African and Asian species of Schistosoma had different gene orders and that the order of genes in the Asian schistosome were more similar to the order observed among flatworms of different genera. The impact of the results from this study is that one can no longer use this important barometer i.e. .mt gene order, for defining phylogenetic relationships without including a diverse sampling of other parasitic groups in the analysis.
Mitochondrial (mt) sequences provide rich sources of data for research in evolutionary biology, population genetics and phylogenetics. During the course of investigating the inter-relationships and biology of a major group of helminth parasites of humans, blood flukes of the genus Schistosoma, we have accumulated extensive data on the mt genomes of these and other parasitic flatworms. As a result, we report that the African flatworms have a mt gene order which is strikingly different from that of other parasitic flatworms including schistosomes from eastern Asia. The magnitude of the differences in gene order between African and Asian Schistosomes is unprecedented among metazoans belonging to the same genus. This result is, nevertheless, consistent with the deep phylogenetic divide between these groups of schistosomes inferred previously from nucleotide sequences. The possibility of major changes occuring even within a single genus indicates that studies using mtDNA gene order for phylogenetic inference should include as diverse a sampling of species within each major taxon as possible.