I am an evolutionary biologist and ichthyologist interested in how ecological dynamics influence evolutionary pattern and process. Much of my research to date has focused on understanding how transitions between major habitats impacts diversification in fishes, with a particular emphasis in the Neotropical regions of South and Central America. The habitat of a species determines the adaptive landscape in which it evolves, and thus is expected to have a profound impact on rates and patterns of morphological and lineage diversification. Different habitats likely vary in rates of lineage diversification due to differences in habitat complexity and the prevalence of barriers. An evolutionary transition in habitat use can alter the trajectory of a lineage by presenting novel ecological parameters and selective pressures and setting new adaptive optima. In aquatic ecosystems most lineages are restricted to either marine or freshwater habitats; biotic interchanges between these habitats are evolutionarily rare due to physiological, ecological, and geological barriers. However, a few groups of fishes have traversed the marine-freshwater boundary over macroevolutionary time scales, providing a unique opportunity to study habitat shifts in aquatic organisms. I use these clades that include both marine and freshwater lineages to better understand the link between ecology, evolution and organismal diversity.