Speciation in Andean rivers: morphological and genetic divergence in the catfish genus Chaetostoma (Teleostei: Siluriformes)

dc.creatorSalcedo, Maurtua Norma
dc.description.abstractDeclining biological diversity and the realization that freshwater is becoming scarce, provide the framework for elevating the priority for taxonomic and biological studies of freshwater organisms. One highly diverse ecosystem, rich in endemic species, is the Andean Montane forest. On the slopes of the Andes the conditions for aquatic life are limited by fast flowing waters and rocky bottoms, which reduce the availability of habitats and resources for many unique forms of live. Nevertheless, the species diversity is high for some fishes such as the catfish genus Chaetostoma. To date there are 45 described species within the genus Chaetostoma, however the type species of the genus has not been used as comparative material in taxonomic studies. Other species are known only from the original description, which all together makes the revision of the genus a model system for studying freshwater montane ecosystems in the Andes. The re-description of two species: Chaetostoma loborhynchos, the type species of the genus, and C. marmorescens, a species with no known type specimen, is suggested after studying their morphology based on available material as the first step towards the revision of the group. Species assigned to the genus Chaetostoma have been considered to have restricted geographic distribution, usually to the basin they inhabit. However, Chaetostoma lineopunctatum was found widely distributed in the Ucayali and Madre de Dios River basins. The presence of cryptic species was tested using morphological divergence, molecular divergence, and phylogenetic structure of samples from both basins. No significant differences were found for morphological divergence (P>0.05) and molecular divergences (1.1%-1.5%) in cytochrome b gene sequences among the localities tested. Phylogenetic structure suggests that the population from the Madre de Dios River basin is more closely related to the Río Tambo population than to the Río Urubamba population. Based on the evidence obtained, these populations are probably the result of recent geographic isolation (~1 Mya) and they should be considered as the same species. Environmental gradients have been suggested as a trigger for speciation. In the mountains of central Peru, two Chaetostoma species live in fast flowing waters of the Río Perené at two different elevation ranges. Chaetostoma lineopunctatum (300-600 m) and C. loborhynhos (1000-1500) were studied to test for phenotype divergence. Geometric morphometric data and interlandmark distances were obtained and analyzed by discriminant analysis. Differences between the phenotypes were significant between the groups (P
dc.publisherTexas Tech Universityen_US
dc.subjectAndean Riversen_US
dc.subjectCatfish genusen_US
dc.titleSpeciation in Andean rivers: morphological and genetic divergence in the catfish genus Chaetostoma (Teleostei: Siluriformes)