According to the biological species concept, species are groups of interbreeding natural populations that are reproductively isolated from other such groups and therefore, hybridization between related species can spontaneously occur, leading to sterile hybrids. Surprisingly, the long-lived turtles are a notable exception of this rule, as distant species, even with more than 40 million years of divergence, are able to hybridize, either in natural environment or in captivity. The topic of this thesis is to summarize the current knowledge on the hybridization of turtles and further explore this phenomenon in a wider phylogenetic spectrum.
