A general classification of New World Leishmania using numerical zymotaxonomy

Area of Science:

• Parasitology
• Molecular Biology
• Evolutionary Biology

Background:

• Leishmania parasites exhibit significant genetic diversity, impacting disease transmission and treatment.
• Accurate classification of Leishmania species is crucial for epidemiological studies and control strategies.

Purpose of the Study:

• To classify New World Leishmania strains using enzyme electrophoresis.
• To determine the phylogenetic relationships between different Leishmania zymodemes.
• To evaluate the taxonomic status of Leishmania subgenera and species complexes.

Main Methods:

• Enzyme electrophoresis of 18 enzymic loci from over 250 Leishmania strains.
• Numerical taxonomy techniques including agglomerative hierarchical clustering, ordination, and cladistics.
• Comparison of New World isolates with 19 reference strains of known Leishmania species.

Main Results:

• 44 distinct zymodemes were identified, clustering into two main groups corresponding to the subgenera Leishmania and Viannia.
• The subgenus Viannia was confirmed as monophyletic, with identified species complexes (L. braziliensis, L. naiffi, L. guyanensis/L. panamensis/L. shawi).
• The subgenus Leishmania was found to be polyphyletic, with New World isolates showing complex evolutionary relationships.

Conclusions:

• The findings support Viannia as a valid taxon and highlight the need for further investigation into the classification of the subgenus Leishmania.
• Leishmania braziliensis and L. naiffi exhibit high polymorphism, whereas L. guyanensis shows remarkable homogeneity across different geographic regions.
• Geographic distribution influences genetic variation, with unique variants of L. guyanensis found only south of the Amazon River.