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Reconstruction of phylogeny by stratophenetic tracing in the fossil record and its comparison with molecular data

Wednesday 5th September 2007 - 09:00 to 10:00
INI Seminar Room 1

The information on the relatedness between taxa and the direction of evolution are only indirectly coded in the input data of all molecular phylogenies. Fossil record, on the other hand, contains direct information on the order, absolute timing and nature of evolutionary events. There is, however, a small hitch: the fossil record only preserves a fraction of the phylogenetically relevant information and it is often so patchy and incomplete, that reconstructions of phylogeny based on fossil data are not superior to molecular methods. A notable exception is presented by the fossil record of marine microplankton, in particular planktonic foraminifera. Their calcite shells are rich in characters and their prolific production and excellent preservation in oceanic sediments produced probably the most complete fossil record on Earth. Here, phylogenetic relationships can be reconstructed by the method of stratophenetic tracing – the nearest one can come to direct observations from a time machine – where both the topology and the timing of divergences are inferred by back-peeling of layers of sediments and tracking changes in morphology of the evolving species through time. The fossil record of planktonic foraminifera thus offers a unique possibility to ground truce molecular phylogenies, the methods that produce them and the assumptions and processes on which the methods are based. We will present a comparison between fossil phylogeny of one monophylum of planktonic foraminifera with corresponding SSU rDNA phylogenies, showing unequivocal direct evidence for long-branch artefacts, enormous differences in substitution rates and incongruent tree topologies, underscoring the potential of foraminifera as a model organism in phylogenetics.

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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons