Monophyletic origin of the genus Sauroleishmania

A 1268-bp DNA fragment representing 25% of the RNA polymerase II largest subunit gene has been used to infer the phylogenetic relationships among four Sauroleishmania species, and their relatedness to the closely related genera Leishmania and Endotrypanum. Comparison of the nucleotide sequences showed that 94% of phylogenetically informative sites occurred at silent codon positions. Distance (neighbor-joining) and weighted parismony analysis of the nucleotide sequence alignment each produced alternate optimal trees which varied in the placement of L. (Viannia) braziliensis and the Sauroleishmania. The cost of branch swapping (number of steps in parsimony analysis) indicated that few steps were required to alternate between these topologies (representing 0.5% of total tree length). In contrast, distance and parsimony analysis of the predicted protein sequence yielded congruent results. The calculated homoplasy, retention and rescaled consistency indices of the protein sequence data indicated that homoplasy was significantly reduced in the protein sequence alignment as compared to the nucleotide sequence alignment. The protein-inferred phylogenies provide strong support for the monophyly of the Sauroleishmania and indicate that these parasites emerged subsequent to the separation of the Leishmania subgenera L. (Leishmania) and L. (Viannia). The close affiliation between Leishmania and Sauroleishmania suggests that the lizard parasites might best be retained in the genus Leishmania.