Historical biogeography of the palaeoendemic toad genus Oreophrynella (Amphibia: Bufonidae) sheds a new light on the origin of the Pantepui endemic terrestrial biota

Aim: Using the Pantepui palaeoendemic toad genus Oreophrynella, we explored (1) the origin of Pantepui endemism and the hypothesis of Pantepui being a source of diversity for the surrounding areas, including the geologically younger Andes; (2) whether early diversification of Oreophrynella conforms with that of Stefania (Hemiphractidae), another Pantepui endemic amphibian, which was recently shown to have vicariantly diverged from Pantepui highlands widespread Oligocene ancestors. Location: The fractured island-like topography of the Pantepui biogeographical region in north-eastern South America. Methods: We inferred the molecular phylogeny of Oreophrynella and other basal Bufonidae genera using three mitochondrial and two nuclear DNA sequences under Bayesian and maximum likelihood methods. We estimated divergence times using a relaxed-clock model and reconstructed ancestral areas through multiple models in a common likelihood framework. Results: Phylogenetic analyses recovered a monophyletic Oreophrynella sister to Atelopus. Biogeographical analyses strongly suggested colonization of Pantepui via a pre-Miocene (Eocene/Oligocene) long-distance dispersal of a proto-Andean ancestor, followed by pre-Quaternary (lower Miocene) vicariant divergences of main lineages, and endemism of these main lineages to distinct biogeographical subunits. Main conclusions: Our results suggest that at least part of the Pantepui diversity stemmed from dispersals from the proto-Andes. Three hypotheses emerge for the origin and evolution of Pantepui endemism, the Distance Dispersal theory, the Plateau theory and the Disturbance-Vicariance theory. Our results indicate that the early diversification of Oreophrynella conforms to that of Stefania, but hint at different factors responsible for the survival or extinction of different tepui summit amphibians.