Evolution of the genus Leishmania as revealed by comparisons of nuclear DNA restriction fragment patterns.

Restriction endonuclease DNA fragment patterns have been used to examine the relationships among 28 isolates of Leishmania as well as Crithidia, Endotrypanum, and Trypanosoma cruzi. Fragments of nuclear DNA were generated with six restriction enzymes, and blots were hybridized with probes from three loci. Among the major lineages the fragment patterns are essentially completely different, while within the major lineages various degrees of divergence are found. Molecular evolutionary trees were constructed using the method of Nei and Li to estimate the percent nucleotide sequence divergence among strains from the fraction of fragments shared. Defined groups, such as species or subspecies within the major lineages, are also grouped by nuclear DNA comparisons. Within the donovani complex, we find Leishmania donovani chagasi and Leishmania donovani infantum to be as similar as strains within Leishmania donovani donovani, consistent with the proposal by other workers that New World visceral leishmaniasis originated quite recently.