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      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


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          Little 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.


          Small 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.


          The 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.


          The 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.

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          The resurrection of oceanic dispersal in historical biogeography.

          Geographical distributions of terrestrial or freshwater taxa that are broken up by oceans can be explained by either oceanic dispersal or vicariance in the form of fragmentation of a previously contiguous landmass. The validation of plate-tectonics theory provided a global vicariance mechanism and, along with cladistic arguments for the primacy of vicariance, helped create a view of oceanic dispersal as a rare phenomenon and an explanation of last resort. Here, I describe recent work that suggests that the importance of oceanic dispersal has been strongly underestimated. In particular, molecular dating of lineage divergences favors oceanic dispersal over tectonic vicariance as an explanation for disjunct distributions in a wide variety of taxa, from frogs to beetles to baobab trees. Other evidence, such as substantial gene flow among island populations of Anolis lizards, also indicates unexpectedly high frequencies of oceanic dispersal. The resurrection of oceanic dispersal is the most striking aspect of a major shift in historical biogeography toward a more even balance between vicariance and dispersal explanations. This new view implies that biotas are more dynamic and have more recent origins than had been thought previously. A high frequency of dispersal also suggests that a fundamental methodological assumption of many biogeographical studies--that vicariance is a priori a more probable explanation than dispersal--needs to be re-evaluated and perhaps discarded.
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              The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system


                Author and article information

                Parasit Vectors
                Parasit Vectors
                Parasites & Vectors
                BioMed Central
                29 October 2013
                : 6
                : 313
                [1 ]Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP 05508-900, Brazil
                [2 ]Departamento de Parasitologia Veterinária, Universidade Federal do Mato Grosso do Sul, Campo Grande, Mato Grosso do Sul, Brazil
                [3 ]Departamento de Patología Veterinaria, Faculdad de Ciencias Veterinarias, Universidad Central de Venezuela, Maracay, Aragua, Venezuela
                [4 ]Faculdade de Agronomia e Medicina Veterinária, Universidade de Brasília, Brasília, DF, Brazil
                [5 ]Caiman Research in Conservation and Management Program, Mamirauá Institute for Sustainable Development, Tefé, Amazonas, Brazil
                [6 ]Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
                Copyright © 2013 Fermino et al.; licensee BioMed Central Ltd.

                This is an open access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                : 31 August 2013
                : 11 October 2013

                crocodilian,trypanosoma evolution,historical biogeography,host-switching,phylogeography,transoceanic dispersion,disjunct distribution,south american river basins


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