Phylogenetics and Historical Biogeography of Otocinclus

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This project will conduct a three year study of the systematics and taxonomy, natural history, and biogeography of the catfishes of the genus Otocinclus. This group of approximately 20 species belongs to one of the largest radiations of freshwater fishes in the Neotropics, the family Loricariidae, which includes over 600 species. These fishes are an important component of the fish fauna of the Atlantic coastal region of southeast Brazil, which includes remnants of the Atlantic Coastal Forest and has been identified as a region of high biodiversity under severe threat of degradation. Relevance of the study of this particular group of fishes lies in their contribution toward understanding the complex historical processes which have shaped the biogeography of organisms inhabiting the Atlantic coastal region of Brazil. Several inherent biological properties, as well as previous work on the group, lend particular significance to study of Otocinclus for achieving these broader goals. Representatives of this group of fishes are presently widely distributed throughout South America, with one or more species occurring in every major river drainage basin. Their small size, coupled with low capabilities for dispersal and wide geographic distribution, predispose them for this kind of biogeographic analysis. Knowledge of the relationships among species of Otocinclus, coupled with similar data for other groups of animals and plants having representatives in the Atlantic coastal region, will provide the basic data for reconstructing the biogeographic history of this particular region and seeking the common causal factors responsible for producing the distributional properties of groups of organisms observed today. This information can then be used to formulate conservation and management strategies. Despite their importance, aspects of the basic biology and taxonomy of these fishes are poorly known; the systematics of this group must be revised, new species described and illustrated, their inter-relationships determined, and present distributions defined before progress in understanding the biogeography of the Atlantic coastal region can be made. Analyses of shape, coloration pattern, and morphological characteristics will be used to determine the taxonomic limits to the species of Otocinclus. Expeditions to two poorly known areas of the Atlantic coastal and neighboring river systems will be undertaken to sample previously undocumented species and to define their distributions. General ichthyological collections will be made and specimens deposited in major museums in both North and South America, forming the material basis for continued study. Laboratory based morphological studies will be used to reconstruct the relationships among Otocinclus species. This project will then provide one additional component toward building a comprehensive dataset for testing competing biogeographic hypotheses in the Neotropical region.