Evolution of neotropical freshwater stingrays and their parasites, taking into account space and time

The purpose of my study was to address the origins and patterns of diversification of Neotropical freshwater stingrays of the family Potamotrygonidae using molecular systematic methods and parasitological data. Phylogenetic analysis of sequences from 12S, 16S, CO I, and cyt-' b' genes combined with 65 morphological characters for 19 terminals suggested that freshwater potamotrygonids are monophyletic and that amphi-American ' Himantura' is their closest marine relative. Phylogenetic analysis of cytochrome-'b' gene for 14 freshwater potamotrygonids generated 2 equally parsimonious trees. Ambiguity occurred in the sister group-relationships among 'Plesiotrygon', ' Potamotrygon yepezi' and an undescribed species from Upper Rio Negro. The differences indicate that 'Potamotrygon' is not a monophyletic group. Molecular clock estimates indicated that the divergence of freshwater potamotrygonids occurred approximately 19 MYA (late Oligocene - early Miocene origin). However, the inclusion of confidence limits suggested that the divergence could have taken place anywhere from 6-38 MYA, ' i.e.', as early as Middle Eocene. The biogeographical analysis based on the phylogeny for freshwater potamotrygonids and six clades of characiform fishes produced six equally parsimonious area cladograms for 14 biogeographical regions within South America. The results, when contrasted with paleogeographical models, suggested that vicariance events due to tectonic episodes, the Miocene seaway, and Plio-Pleistocene Amazon Lagoon all imposed patterns of diversification on these components of the Neotropical fauna. For the parasites studied, three new genera of phyllobothriid cestodes were erected. 'Aseptobothrium' gen. n. was erected to receive ' Caulobothrium anacolum' inhabiting 'Himantura schmardae' from the Caribbean. In addition, two unusual phyllobothriids inhabiting freshwater potamotrygonids were also erected: 'Anindobothrium' gen. n., and 'Plesiorhinebothroides' gen. n. Finally, a taxonomic review of 'Rhinebothroides' was provided, in which four species were recognized: 'R. freitasi', 'R. glandularis', ' R. moralarai', and 'R. scorzai'. A phylogenetic analysis of selected genera of phyllobothriids based on 20 morphological characters for 17 terminal taxa generated 28 equally most parsimonious trees. The strict consensus resolved three clades: (i) ' Aseptobothrium' + 'Anindobothrium', (ii) (' Caulobothrium' ('Rhadbotobothium' + 'Rhinebothroides ')), and (iii) 'Plesiorhinebothroide's + ' Rhinebothroides'. 'Anthocephalum' was considered paraphyletic. Successive weighting resolved the following topology for 'Rhinebothroides ': ('R. freitasi' ('R. glandularis' ('R. moralarai' + 'R. scorzai'))). A taxonomic review of the onchobothriid genus 'Potamotrygonocestus ' was presented in which six species were recognized. 'Potamotrygonocestus orinocoensis' was considered junior synonym of 'P. travassosi ', and 'P. chaoi', 'P. fitzgeraldae', and 'P. maurae' were described as new species. Phylogenetic analysis of six morphological characters generated a single phylogenetic hypothesis: ('P. maurae' (('P. amazonensis' + 'P. magdalenensis')('P. chaoi' ('P. fitzgeraldae ' + 'P. travassosi')))). The biogeographical analysis of selected clades of parasites and belonid fishes suggested that the areas which today comprise the Eastern Pacific and the Caribbean were once a single biogeographical component, and that divergence of the South America freshwater fauna occurred prior to the divergence of the eastern Pacific from the Caribbean and other areas in the Atlantic. This result coupled with molecular clock estimates suggested that freshwater potamotrygonids and neotropical freshwater belonid fishes diverged from their marine ancestor during the Early-Mid Miocene northern marine incursion into South America.