A revised molecular phylogeny reveals polyphyly in Schistura (teleostei: Cypriniformes: nemacheilidae

With more than 215 presently known species, the genus Schistura dominates the loaches with a vast range of species and morphological diversity. Loaches as a whole comprise a large portion of the order Cypriniformes with an estimated 1200 species. However, the evolutionary relationships of the majority of loaches remain unresolved. Most species descriptions are based exclusively on morphological data and a limited number of loaches have been included in molecular phylogenies. This has led to inconsistencies between their taxonomy and evolutionary relationships, as many species have similar environments, life histories, and markings. Because of the great diversity in species and morphology, this thesis provides a broader understanding of loach taxonomy and phylogenetics while testing the utility of morphological data to infer phylogenetic relationships. A current phylogeny of Schistura loaches compiled by the Cypriniformes Tree of Life project indicates this group is polyphyletic. Therefore, it is paramount to include additional species, especially those recently described, into a phylogenetic analysis to obtain a stable taxonomy at the generic level. For this study, I contributed data of nine members of the genus Schistura via mitochondrial gene fragments to assess their evolutionary relationships among other loach taxa. In particular, this research includes several novel species contributing knowledge about the evolutionary history of these underrepresented Asian freshwater fishes. Their great diversity reflects the significant number of isolated environments in which they occur. These data not only add to scientific knowledge of genetic diversity but lend more supporting evidence for developing nations to protect their natural resources in order to conserve these newly discovered species.