Speculations on the origin and evolution of the genus Leishmania

Recently two hypotheses have been proposed for the evolution of Leishmania involving respectively a Neotropical or Paleartic origin for the species. H ere an alternative proposal on the phylogeny of Leishmania based on the maj or divisions within the genus is presented. In this hypothesis a Neotropic origin is retained for L. (Viannia) and Paraleishmania, a recently desribed section within the genus Leishmania, while an African origin is proposed f or L. (Leishmania) and possibly Sauroleishmania. The current distribution o f Leishmania in the Neotropics is explained as the product of multiple intr oductions of Leishmania parasites into the New World. Problems with organis mal identity in Sauroleishmania and the use of molecular sequence data in i nferring phylogenies are also discussed.