Speciation in freshwater environments: Testing for multiple radiations in African Synodontis catfish

Understanding the processes that underlie speciation is fundamental to explaining the diversity of life. Yet, life on Earth is not evenly distributed, so that some groups of organisms contain many more species than others, while some environments are a hotbed for promoting unique species diversity. The tropical lakes of Africa's rift valley, considered to be hotspots of biodiversity, are such environments and provide evolutionary biologists with a unique opportunity to study the evolutionary mechanisms responsible for species formation. By studying species rich faunal lineages that span both lacustrine and riverine environments, it will be possible to not only further our knowledge of processes leading to species radiations within lakes, but determine the extent to which lake environments have influenced the genetic diversity of species within African rivers. Furthermore, a broad species distribution also allows biologists to examine whether past geological or climatic events have had an impact on the current patterns of biodiversity, which may help us make future predictions regarding biodiversity and therefore their conservation. The highly diverse catfish genus Synodontis, containing c.120 species, is selected here, to investigate the factors influencing biological diversity in freshwater environments, as it meets all these criteria. Using DNA data from Synodontis catfish collected across Africa, combined with fossil dates, we shall be able to reconstruct the evolutionary history of their relationships. This will be important as it will enable us to determine if certain species groups evolved within lake basins and whether speciation in these environments happened faster than in rivers. We are also interested to see whether there might be morphological differences in body shape for example, associated with shifts between different aquatic realms. Finally, we will examine geographic patterns to test whether tectonic rifting events, or drier periods in Africa's climate have influenced the evolution of Synodontis catfish. The results of this study can then be compared with other freshwater faunas in order to find generalities that will help us to better understand the processes that have promoted current biodiversity of tropical freshwaters. This study provides a unique and feasible opportunity to examine diversification in this species-rich group, as we are fortunate that the majority of tissue samples are collected and available to begin work upon.