Freethought & Rationalism Archive

MrDarwin · 03-06-2003, 01:10 PM

Very cool article appeared recently in Nature discussing the mammals of Madagascar, particularly the carnivores, none of which are found anywhere else on earth. A molecular analysis of the carnivores of Madagascar strongly suggests that the group originated from a single ancestor that somehow arrived on the island from Africa, millions of years ago but long after the separation of the two land masses. A similar origin is postulated for the primates of Madagascar, but which are postulated to have arrived millions of years earlier.

Yoder et al. 2003, "Single origin of Malagasy Carnivora from an African ancestor", Nature 421: 734 - 737.

Abstract:

Quote:

The Carnivora are one of only four orders of terrestrial mammals living in Madagascar today. All four (carnivorans, primates, rodents and lipotyphlan insectivores) are placental mammals with limited means for dispersal, yet they occur on a large island that has been surrounded by a formidable oceanic barrier for at least 88 million years, predating the age of origin for any of these groups. Even so, as many as four colonizations of Madagascar have been proposed for the Carnivora alone. The mystery of the island's mammalian origins is confounded by its poor Tertiary fossil record, which leaves us with no direct means for estimating dates of initial diversification. Here we use a multi-gene phylogenetic analysis to show that Malagasy carnivorans are monophyletic and thus the product of a single colonization of Madagascar by an African ancestor. Furthermore, a bayesian analysis of divergence ages for Malagasy carnivorans and lemuriforms indicates that their respective colonizations were temporally separated by tens of millions of years. We therefore conclude that a single event, such as vicariance or common dispersal, cannot explain the presence of both groups in Madagascar.

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