Dergam, Jorge A., authorBehnke, Robert, advisorBlack, William C., IV, committee memberKondratieff, Boris C., committee memberFausch, Kurt D., committee memberStack, Stephen, committee member2017-06-232017-06-231996http://hdl.handle.net/10217/181882I analyzed patterns of congruence of independent data sets (molecular and karyotypical) within the Neotropical fish species complex Hoplias ma/abaricus Bloch, 1794, at the local and at the macrogeographic levels. In two locales of sympatry of fish with different karyotypes (cytotypes) in Argentina and Brazil, the patterns of congruence were interpreted as evidence that the cytotypes are distinct species.At the macrogeographical level, I analyzed the patterns of congruence of nuclear DNA, mitochondrial DNA and cytogenetic data. In the Rio Iguassu, the patterns of similarity of nuclear DNA markers (Randomly Amplified Polymorphic DNA) suggested that the population of H. malabaricus of this river derives from a southern-southwestern group of populations. At the continental level, nuclear DNA markers were consistent with other data sets at low levels of genetic divergence, allowing for geographic analysis of differentiation of populations and for the detection of cryptic sympatric forms. However, similarity analysis based on these markers failed to recover phylogenetic relationships as evidenced by mitochondrial DNA sequence analysis. Phylogenetic analyses of mitochondrial DNA sequences indicated high levels of within and among population variation. In the best supported tree, a mitochondrial DNA variants (haplotype) from the middle Rfo Parana derived from populations with 40 chromosomes is the sister group of all the other haplotypes of Hoplias malabaricus, while populations in southeastern and southern Brazil with 2/7=42 form a monophyletic clade within the complex. The pattern of geographic distribution of this clade is compatible with other, unrelated fish taxa. However, other haplotypes from populations with 2/7=42 were phylogenetically more related to haplotypes from populations with 2/7=40. Thus, grouping populations of the species complex by diploid numbers would render those groups paraphyletic (they would not include all descendants of a common ancestor). The discrepancy of patterns of variation between diploid number and mitochondrial DNA may be explained by multiple origins of diploid numbers, or by random fixation of ancestral polymorphisms following the fixation of chromosomal rearrangements in a large population.doctoral dissertationsengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.biogeographyfish communitiesFreshwater fishes -- Geographical distributionBiogeographyFish communitiesText