The phylogeography of trypanosomes from South American alligatorids and African crocodilids is consistent with the geological history of South American river basins and the transoceanic dispersal of Crocodylus at the Miocene

Bruno R Fermino,Patrick B Hamilton,Catia D De Paula,Robinson Botero-Arias,Marta Campaner,Herakles A Garcia,Carmen S A Takata,Fernando Paiva,Erney P Camargo,Marta Mg Teixeira,Laerte B Viola

doi:10.1186/1756-3305-6-313

Abstract

BackgroundLittle is known about the diversity, phylogenetic relationships, and biogeography of trypanosomes infecting non-mammalian hosts. In this study, we investigated the influence of host species and biogeography on shaping the genetic diversity, phylogenetic relationship, and distribution of trypanosomes from South American alligatorids and African crocodilids.MethodsSmall Subunit rRNA (SSU rRNA) and glycosomal Glyceraldehyde Phosphate Dehydrogenase (gGAPDH) genes were employed for phylogenetic inferences. Trypanosomes from crocodilians were obtained by haemoculturing. Growth behaviour, morphology, and ultrastructural features complement the molecular description of two new species strongly supported by phylogenetic analyses.ResultsThe inferred phylogenies disclosed a strongly supported crocodilian-restricted clade comprising three subclades. The subclade T. grayi comprised the African Trypanosoma grayi from Crocodylus niloticus and tsetse flies. The subclade T. ralphi comprised alligatorid trypanosomes represented by Trypanosoma ralphi n. sp. from Melanosuchus niger, Caiman crocodilus and Caiman yacare from Brazilian river basins. T. grayi and T. ralphi were sister subclades. The basal subclade T. terena comprised alligatorid trypanosomes represented by Trypanosoma terena n. sp. from Ca. yacare sharing hosts and basins with the distantly genetic related T. ralphi. This subclade also included the trypanosome from Ca. crocodilus from the Orinoco basin in Venezuela and, unexpectedly, a trypanosome from the African crocodilian Osteolaemus tetraspis.ConclusionThe close relationship between South American and African trypanosomes is consistent with paleontological evidence of recent transoceanic dispersal of Crocodylus at the Miocene/Pliocene boundaries (4–5 mya), and host-switching of trypanosomes throughout the geological configuration of South American hydrographical basins shaping the evolutionary histories of the crocodilians and their trypanosomes.

Highlights

Little is known about the diversity, phylogenetic relationships, and biogeography of trypanosomes infecting non-mammalian hosts
Previous phylogenetic analysis restricted to a few crocodilian trypanosomes hampered any attempt to evaluate species richness, and to infer biogeographical scenarios underlining the evolutionary history of crocodilian trypanosomes [8,9,12,21]
Isolation in culture and growth behaviour We collected blood from crocodilians captured in four South American river basins: PP, AM, AT and OR (Figure 1; Table 1) and characterized 5 new cultures: two from Ca. yacare (TCC1611, 1974), two from Ca

Summary

Introduction

Little is known about the diversity, phylogenetic relationships, and biogeography of trypanosomes infecting non-mammalian hosts. We investigated the influence of host species and biogeography on shaping the genetic diversity, phylogenetic relationship, and distribution of trypanosomes from South American alligatorids and African crocodilids. The evolutionary histories of trypanosomes from mammals of distinct orders and from other vertebrate classes only recently began to be addressed [11,12,13,14,15,16,17,18,19]. In Africa, trypanosomes of Crocodylus niloticus, Mecistops cataphractus and Osteolaemus tetraspis were all named T. grayi [22,23], a species that has been commonly described in its vector tsetse flies [24,25,26,27]. Previous phylogenetic analysis restricted to a few crocodilian trypanosomes hampered any attempt to evaluate species richness, and to infer biogeographical scenarios underlining the evolutionary history of crocodilian trypanosomes [8,9,12,21]

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Conclusion