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How many characters are needed to recontruct the true tree?

Presented by: 
M Fischer [Canterbury]
Monday 17th December 2007 - 15:50 to 16:10
INI Seminar Room 1
Session Chair: 
Kathi Huber

Maximum Parsimony, which basically favors the tree hypothesizing the fewest number of character state changes, is still one of the most important methods of tree reconstruction. Even so, MP is known to be prone to fail when the underlying phylogenetic tree has some extreme characteristics, as it is the case, for example, in the Felsenstein-zone or when interior edges are very short. While the Felsenstein-zone has already been well-examined over the years, some aspects of the latter problem remained unsolved. We investigated this on a binary unrooted 4-taxon phylogenetic tree with a short interior edge and pending edges of multiple length. In my talk, I will present an optimal branch length of the interior edge in this scenario and I will explain how many characters are at least needed to reconstruct the ‘true’ tree. Furthermore, we investigated some more properties of MP and found that for some trees, MP performs better when only a subset of the given set of taxa is considered. I will show such a phylogenetic tree and explain, for instance, why for a subset of size 1, i.e. a single leaf, this surprising scenario cannot happen.

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