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PhD defense - Sebastian Höhna 29/11, 10:00, SU

posted Nov 15, 2013, 4:35 AM by Johan Nylander   [ updated Nov 15, 2013, 4:38 AM ]
Upcoming PhD defense in Stockholm (Academic dissertation for the Degree of Doctor of Philosophy in Mathematical Statistics at Stockholm University)!

Title: Bayesian Phylogenetic Inference - Estimating Diversification Rates from Reconstructed Phylogenies

By: Sebastian Höhna

Opponent: Prof. Ziheng Yang, University College London

When: Friday 29 November 2013 at 10:00

Where: Sal 14, hus 5, Kräftriket, Roslagsvägen 101.


Phylogenetics is the study of the evolutionary relationship between species. Inference of phylogeny relies heavily on statistical models that have been extended and refined tremendously over the past years into very complex hierarchical models. Paper I introduces probabilistic graphical models to statistical phylogenetics and elaborates on the potential advantages a unified graphical model representation could have for the community, e.g., by facilitating communication and improving reproducibility of statistical analyses of phylogeny and evolution.
Once the phylogeny is reconstructed it is possible to infer the rates of diversification (speciation and extinction). In this thesis I extend the birth-death process model, so that it can be applied to incompletely sampled phylogenies, that is, phylogenies of only a subsample of the presently living species from one group. Previous work only considered the case when every species had the same probability to be included and here I examine two alternative sampling schemes: diversified taxon sampling and cluster sampling. Paper II introduces these sampling schemes under a constant rate birth-death process and gives the probability density for reconstructed phylogenies. These models are extended in Paper IV to time-dependent diversification rates, again, under different sampling schemes and applied to empirical phylogenies. Paper III focuses on fast and unbiased simulations of reconstructed phylogenies. The efficiency is achieved by deriving the analytical distribution and density function of the speciation times in the reconstructed phylogeny.

Johan Nylander,
Nov 15, 2013, 4:37 AM