Trypanosomes are monophyletic: evidence from genes for glyceraldehyde phosphate dehydrogenase and small subunit ribosomal RNA

Kinetoplastid phylogenetics, with special reference to the evolution of parasitic trypanosomes

“…E-mail: j.r.stevens@ex.ac.uk 2000) and even in those parasites of medical importance, it is little more than a decade since the widespread introduction of DNA sequencing technologies has allowed the evolution of parasitic trypanosomatids (and kinetoplastids in general) to be evaluated by formal phylogenetic analysis (Fernandes et al, 1993;Alvarez et al, 1996;Maslov et al, 1996;Lukes et al, 1997;Haag et al, 1998;Hannaert et al, 1998;Stevens et al, 1999Stevens et al, , 2001Wright et al, 1999;Hamilton et al, 2004;Moreira et al, 2004). To fully understand the evolutionary history of parasitic kinetoplastids and to understand the context within which the evolution of each parasite group has unfolded, an understanding not just of the parasites, but also of broader kinetoplastid phylogenetics is required.…”

“…2) supported monophyly. However, Hamilton et al (2004) also demonstrated that different large (> 68 taxa) 18S rDNA sequence alignments can either strongly support or reject monophyly depending on the range of taxa and the characters included in each analysis, so, while trypanosome monophyly appears highly probable, no definitive conclusion can be reached using this gene. Confidence in 18S rDNA sequence data to infer phylogenetic relationships has also been challenged by the observation of two distinct copies of these genes in T. cruzi and other trypanosomatids (Stothard et al, 1998).…”

“…Confidence in 18S rDNA sequence data to infer phylogenetic relationships has also been challenged by the observation of two distinct copies of these genes in T. cruzi and other trypanosomatids (Stothard et al, 1998). In contrast, phylogenetic studies based on proteincoding genes (Hannaert et al, 1992(Hannaert et al, , 1998Hashimoto et al, 1995;Adjé et al, 1998;Simpson et al, 2002) have consistently and unequivocally supported monophyly, a conclusion strongly supported by Hamilton et al (2004) in their recent analyses of both glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) DNA and protein trees from a broad range of trypanosomatid taxa, rooted using Euglena gracilis, an unequivocal outgroup taxon. Trypanosome monophyly is further supported by the phylogenies of Simpson et al (2002) based on heat shock protein 90 amino acid sequences that include a different range of kinetoplastid taxa to the gGAPDH gene trees.…”

“…A monophyletic group consists of taxa that are descended from a single common ancestor and contains all known descendants from that ancestor. The first molecular phylogenetic studies, based on comparisons of mitochondrial and nuclear ribosomal DNAs (rDNA), showed trypanosomes to be paraphyletic (Gomez et al, 1991;Fernandes et al, 1993;Maslov et al, 1996), while subsequent rDNA-based studies, which have included more taxa from a far broader range of host species (Lukes et al, 1997;Stevens et al, 1999Stevens et al, , 2001Wright et al, 1999;Simpson et al, 2002;Hamilton et al, 2004) (Fig. 2) supported monophyly.…”

“…For example, although usually transmitted by bloodsucking triatomine bugs, T. cruzi can be transmitted during breast-feeding (Miles, 1979) and T. equiperdum is transmitted during coitus between equines (Hoare, 1972). Evidence from the recent broad gGAPDH gene phylogeny of Hamilton et al (2004) also indicates that the trypanosome clade arises from within the wider group of trypanosomatids, which are parasites of insects (some of which have an additional vertebrate or plant host). Thus, the most likely ancestor of extant trypanosomes was an insect trypanosomatid parasite.…”