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Ranked tree shapes, shuffles, and a new test for neutrality

Date: 
Wednesday 19th December 2007 - 10:00 to 10:20
Venue: 
INI Seminar Room 1
Session Chair: 
Elizabeth Allman
Abstract: 

Phylogenetic tree shapes are an established object of study, and have proven useful for testing macroevolutionary hypotheses. However, tree shapes are typically considered without branch length information, which eliminates a considerable amount of useful data. We propose the use of ``ranked'' phylogenetic tree shapes-- tree shapes such that the order of diversification events is specified-- to test macroevolutionary hypotheses. We describe two classes of null models on ranked tree shapes, and then propose a test for deviation from these models. In particular, our test rejects the null hypothesis when relative rates of diversification for two daughter clades change over time. Thus, we consider the test as looking for evidence of ``bursting'' diversification on one hand, or ``refractory'' diversification on the other. Our test rejects neutral evolution for a sample of sequences of the Hepatitis C virus which will be discussed.

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