Investigating the role of hybridization in the evolution of the genus Corydoras

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Hybridization, where two species mate and produce offspring is being increasingly recognised as having an important role in the evolution of new species and even groups of species. It has been implicated in the evolution of the Hawaiian crickets, the Lake Baikal sculpins and the African lacustrine cichlids (three radiations of several hundred species each) to name but three. In this study I will investigate the role hybridization has played in the evolution of a group of South American catfish, many of which have undergone a doubling of their DNA at some point in their evolutionary history. I will determine the sequences of mitochondrial DNA genes (which are inherited solely from the mother), and nuclear genes, for which a copy is inherited from the father and the mother. The relationships between species will then be determined using differences in these DNA sequences. In species in which hybridization has occurred, DNA sequences from both the parental species should be present at nuclear genes, and this may allow the evolutionary history of which species have hybridised to produce new species to be determined. Microsatellite markers will also be used to investigate the minimum ploidy level of each taxa in order to determine whether the genome of each species has been doubled in its evolutionary history.