Phylogenetic and biogeographical analyses were performed for the Plesiolebiasini, a group of 20 small and rare species of South American annual killifishes, some threatened with extinction, occurring in river basins of Brazil, Bolivia, Paraguay, and Argentina. The results of a maximum parsimony analysis of 142 morphological characters highly corroborate monophyly of the Plesiolebiasini. Monophyly of each plesiolebiasine genus is supported and Plesiolebias is hypothesized to be the sister group to a clade comprising the remaining plesiolebiasine genera (Papiliolebias, Pituna, Maratecoara, and Stenolebias), corroborating studies based on mitochondrial genes. The phylogenetic analysis supports sister group relationships between Papiliolebias and the clade containing Pituna, Maratecoara, and Stenolebias, and between Maratecoara and Stenolebias. The biogeographical analysis indicates a complex historical biogeographical scenario for plesiolebiasines. A vicariance event between the western Paraguay area and northern river basins may be related to the isolation of the Chaco region from the Amazon between the Late Oligocene and Early Miocene. A vicariance event involving the Paraguay River basin and northern rivers, and the multiple occurrence of area hybridism along the Araguaia depression are tentatively identified as a consequence of tectonic subsidence events occurring during the Pleistocene.
© 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162, 131–148.