The historical Biogeography of Mammalia

Today, Sarita will present a paper on historical biogeography of mammals. The authors proposed to identify the origins of the different groups of mammals by comparing nine different methods for reconstructing ancestral areas including data on phylogenies, divergence times and ancestral areas reconstructions. This approach shows that both dispersal and vicariance triggered diversification of mammals. Thanks Sarita.

From MS Springer, RW Meredith, JE Janecka and WJ Murphy, Philosophical Transactions of the Royale Society B, (2011) 366, 2478–2502 [doi:10.1098/rstb.2011.0023]


Title: The historical biogeography of Mammalia

Abstract. Palaeobiogeographic reconstructions are underpinned by phylogenies, divergence times and ancestral area reconstructions, which together yield ancestral area chronograms that provide a basis for proposing and testing hypotheses of dispersal and vicariance. Methods for area coding include multi-state coding with a single character, binary coding with multiple characters and string coding. Ancestral reconstruction methods are divided into parsimony versus Bayesian/likelihood approaches. We compared nine methods for reconstructing ancestral areas for placental mammals. Ambiguous reconstructions were a problem for all methods. Important differences resulted from coding areas based on the geographical ranges of extant species versus the geographical provenance of the oldest fossil for each lineage. Africa and South America were reconstructed as the ancestral areas for Afrotheria and Xenarthra, respectively. Most methods reconstructed Eurasia as the ancestral area for Boreoeutheria, Euarchontoglires and Laurasiatheria. The coincidence of molecular dates for the separation of Afrotheria and Xenarthra at approximately 100 Ma with the plate tectonic sundering of Africa and South America hints at the importance of vicariance in the early history of Placentalia. Dispersal has also been important including the origins of Madagascar’s endemic mammal fauna. Further studies will benefit from increased taxon sampling and the application of new ancestral area reconstruction methods.