Molecular evolution and phylogeny of leishmania

The genus Leishmania was first described in 1903. Various numbers of species have been described since then. Although recent hierarchical taxonomic schemes have increasingly used intrinsic characters to assign Leishmania organisms into different species, they are still heirs of the first classifications based primarily on extrinsic characters. The current classification system, which proposes up to 35 species, is based on multilocus enzyme electrophoresis which is still the reference technique for the identification of Leishmania species. Molecular phylogenies of Leishmania suggest that the number of species may be too large. Furthermore, it is still controversial whether the genus Leishmania appeared first in the Old World or in the New World although several rooted sequenced-based phylogenies favor a neotropical origin. Many molecular markers have demonstrated substantial intraspecies diversity and the existence of geographically and genetically isolated populations in all Leishmania species tested so far. A predominantly clonal evolution has been proposed for Leishmania with rare sexual recombination events. This hypothesis has repeatedly been challenged by the detection of hybrids, mosaic genotypes, and gene flow between populations, strong inbreeding and, finally, the detection of genetic recombination under laboratory conditions. This chapter reviews the recent (mostly) molecular data that provide new insights into the evolution, taxonomy, phylogenetic, and population genetic relationships of Leishmania, but also the questions raised by this knowledge. It also discusses the power of modern approaches, such as multilocus sequence typing and multilocus microsatellite typing for studying the inter-and intraspecies variation of Leishmania parasites.