Niche diversification of Mediterranean and southwestern Asian tortoises

BACKGROUND: Tortoises of the genus Testudo are widely distributed throughout the Mediterranean region and southwestern Asia. However, the evolutionary mechanisms of diversification in this genus are still poorly understood. METHODS: In this study, we assessed the evolutionary patterns in the climate niches of five species and 11 subspecies of the genus Testudo using ecological niche models and evaluated the niche overlap based on species phylogenetic distances. RESULTS: The ecological models indicated that most species differ in their climate niches, but show overlap, with gradual transitions at range boundaries. As expected, the ecological divergence among subspecies was lower than that among species. Evaluation of the phylogenetic signal indicated that climate niches have been weakly conserved, but sister species also show high evolutionary divergence.