Molecular Investigations of the Diversity of Freshwater Fishes across Three Continents

Abstract

Fishes are the most speciose vertebrates, and incredible diversity can be found within different groups of fish. Due to their physiological limitations, fish are confined to waters, and in freshwater fish, this is restricted to lakes, rivers, and streams. With a constrained habitat like a freshwater system, it can be expected that freshwater fish will show varying levels of diversity depending on a suite of characteristics. Within this dissertation, I examine the diversity of three fish groups: the speciose Enteromius of West Africa, the population genetic diversity of Pteronotropis euryzonus in Alabama and Georgia, and the unexpectedly species rich Trichomycterus from the Guyana highlands. I use molecular methods and geometric morphometrics to determine the systematics of the species and uncover the hidden diversity within their respective groups. When it comes to diversity, the small barbs of Africa are vastly understudied and require a taxonomic revision. From that revision, a better understanding of the diversity leads to a new genus description. For the small-bodied minnow Pteronotropis, moving across a river was believed to be unlikely. Highland catfishes like Trichomycterus were believed to be limited not only in their dispersal ability, but also in their diversity. The diversity of freshwater fishes is reflected within the chapters of this dissertation.