Discussion

The genus Leishmania includes ~53 species, 20 of which cause human leishmaniais, a significant tropical disease that has afflicted humans for millennia. But how ancient is Leishmania and where did it arise? Some suggests it originated in the Palearctic. Others suggest it appeared in the Neotropics. The Multiple Origins theory proposes that separation of Old World and Neotropical species occurred following the opening of the Atlantic. The Supercontinents hypothesis suggests Leishmania evolved on Gondwana 140-90 million years ago (MYA). We performed a detailed molecular and morphological characterisation of a novel Australian trypanosomatid. It was confirmed as a sister to the Neotropical Leptomonas costaricensis, and designated as Leptomonas australis sp. nov. Assuming L. costaricensis and L. australis split when Australia and South America separated, their divergence occurred 41-36 MYA. Using this event as a calibration point for a phylogenetic time tree, Leishmania was estimated to have appeared ~92 MYA. Ultimately, this study contributes to our understanding of Leishmania origins by independently supporting the Supercontinent hypothesis.