The biogeography of extant lungfishes traces the breakup of Gondwana

Aim: Lungfishes are one of the two surviving clades from the once diverse grade of lobe-finned fishes leading to tetrapods. This classic living fossil lineage, which is the living sister to four-limbed terrestrial vertebrates, appeared approximately 425 million years ago and rapidly diversified. However, the evolution of lungfishes after their initial radiation is poorly understood, and whether their present distribution tracks ancient geographical change is a classic problem in biogeography. Location: Global. Taxon: Lungfishes (Dipnoi). Methods: Here, we combine mitogenomic, nuclear gene and fossil data to reconstruct the timing of lungfish diversification a Bayesian tip-dating approach to quantitatively test hypotheses of lungfish historical biogeography and divergence times. We sample all major living and extinct lungfish lineages, including three of the four species of African lungfishes (Protopterus spp.), the Australian lungfish Neoceratodus forsteri, the South American lungfish Lepidosiren paradoxa and 13 fossils representing extinct lineages from across the globe. Results: Our results demonstrate that the divergences of the three major living lungfish clades closely recapitulate the stepwise fragmentation of the Gondwana during the Mesozoic. All of our model-based biogeographical reconstructions support a Gondwanan vicariance model for the origins of the present distribution of lungfish lineages. Conclusions: In turn, lungfishes provide an excellent example of how the integration of fossil data may drastically change support for historical biogeographical hypotheses previously discounted by molecular data and are one of the few living animal lineages that record incredibly ancient geographical changes in their phylogeny.