Diversity and phylogeny of insect trypanosomatids based on small subunit rRNA genes: Polyphyly of Leptomonas and Blastocrithidia

With the aim of further investigating phylogenetic relationships in insect trypanosomatids, we have determined the sequences of small subunit rRNA gen es from ten isolates, which were originally classified as Leptomonas. Blast ocrithidia, and Wallaceina based on their morphology in the hosts. The infe rred maximum likelihood, parsimony, and distance trees indicate that the Le ptomonas and Blastocrithidia are polyphyletic, and confirm the polyphyly of Herpetomonas and Crithidia. Blastocrithidia triatoma and Leptomonas collos oma were among the earliest branching lineages among the insect trypanosoma tids. while most other isolates were found within a closely related termina l clade, which also included Crithidia fasciculata. This analysis has clear ly demonstrated that the morphological classification system of insect tryp anosomatids does not always reflect their genetic affinities warranting its revision in the future.