Evolution of parasitism in kinetoplastid protozoa

Molecular phylogeny has provided a new insight on the almost century-old discussion on the origin of parasitism in kinetoplastid protozoa. Phylogenetic trees constructed on the basis of ribosomal RNA sequences show that digenetic parasites (which alternate between insect vector and vertebrate host) did not descend from the same common ancestor. Lineages of Trypanosoma appeared early in evolution and descended directly from an ancestral trypanosomatid, while lineages of Leishmania and Endotrypanum separated late from monogenetic parasites. Here, Dmitri Maslov and Larry Simpson discuss how these new results have changed our view of the evolution of parasitism.