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Vicariance and trans-oceanic dispersal in mammals and plants

Andrew Rodrigues supervised by Prof. Emmanuel Douzery and Prof. Doyle McKey
University Montpellier II, IFR119 Continental, Mediterranean, and Tropical Biodiversity

There are two distinct camps within the field of biogeography, that of the vicariance biogeographer and that of the dispersalist. With the increasing wealth of evidence in the 20th century for the existence of continental drift as a result of plate tectonics, it seemed more parsimonious to believe that present day distributions of faunas were a result of ancient vicariance events rather than chance dispersal ones. A classic example of this is in the case of Gondwana. The supercontinent Gondwana comprised of present-day South America, Africa, Australia, New Zealand, Antarctica and India. Taxa with present-day distributions solely within these regions were assumed to provide support for the break up of this supercontinent approximately 150 Mya; equally, it was this vicariance event that was assumed to explain their present-day distributions. Molecular evidence however, seems to be to the contrary.

In this PhD I will be looking specifically at the South America/Africa split and at taxa that demonstrate this distribution. Splits between Platyrrhini, New World monkeys and Catarrhini, Old World monkeys; Caviomorpha, South American rodents and Phiomorpha, Old World rodents; and angiosperm families that demonstrate the same disjunction will be analysed using new molecular markers. These phylogenies will then be dated and compared against date estimates of the Gondwana split and against each other. If, there is corroboration between dates for each of the different groups, then there is evidence that there was one split that affected all taxa i.e. a vicariance event. If however, there is no corroboration between dates then, we must infer dispersal as the primary means by which colonisation of the continents occurred and, if it was dispersal, how did this dispersal occur? Were there landbridges between Africa and South America? Have there been multiple colonisations in both directions?

I will look then, at the relative roles of vicariance and dispersal in the colonisation of areas for a range of mammal and plant taxa, and will ultimately aim to answer the million-dollar question, 'How far, can a monkey swim?'

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