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Phylogenetic rate heterogeneity and evolution in filmy ferns hymenophyllaceae)

PI(s): Sabine Hennequin (University of Paris)
Start Date: 5-Nov-2007
End Date: 17-Nov-2007
Keywords: genomics, phylogenetics, software, life histories

Evidence for phylogenetic rate heterogeneity across the Tree of Life has steadily emerged in recent years. Explanations for the observed rate differences have ranged from mutational processes to whole organism effects, but in most studies these explanations remain mere hypotheses, and are usually unknown. Within filmy ferns, phylogenetic studies of plastid rbcL sequences have revealed extreme branch length differences between the two major clades (trichomanoids and hymenophylloids). The significance of these differences has not been explained and the factors responsible have not been identified. This rate heterogeneity phenomenon raises two broad questions: 1) is this a generalized pattern also present in the nuclear and mitochondrial genomes? and 2) how can it be explained? By analyzing sequence data that is already in hand with new and developing software, we propose to answer the first question. The second question requires an improved knowledge of filmy fern life history. To this end, we will estimate divergence times for the family, then reconstruct ancestral changes in morphology, ecology and life history patterns that may correlate with the observed rate differences, and that perhaps impacted the diversification of filmy ferns.