Reconciling fossils and molecules: Cenozoic divergence of cichlid fishes and the biogeography of Madagascar
The biogeographical origins of the extant vertebrates endemic to Madagascar are largely unsolved, but have often been related to vicariance in the context of fragmentation of the supercontinent Gondwana in the Mesozoic. Such hypotheses are especially appealing in the case of cichlid fishes, which show phylogenetic relationships reflecting the temporal successions of the breakup of Gondwana. We used molecular clock data to test this assumption.Location
Fragments of the 16S rRNA gene and of the nuclear Tmo-4C4 locus, partly obtained from Genbank from South American, African, Malagasy and Indian cichlids were analysed.Methods
Based on monophyletic cichlid radiations in African lakes, we calibrated a molecular clock. The obtained rates were used to estimate the age of divergence of the major cichlid clades.Results
The results agreed better with a Cenozoic than with a Mesozoic divergence, and were in accordance with the fossil record. Sequence divergences of the 16S and 12S rRNA genes of most lineages of Malagasy terrestrial and freshwater vertebrates from their non-Malagasy sister groups were below saturation and many were relatively similar to those of cichlids.Main conclusions
A Cenozoic dispersal from continental landmasses may explain the origin of most extant Malagasy vertebrate groups better than a Jurassic/Cretaceous vicariance.