Speaker: Serkan Hosten, San Francisco State University
Title: UPGMA, the space of all phylogenetic trees, and tree reconstruction
Abstract: In this talk I will give an introduction to constructing a phylogenetic tree from "distance data" that measures the pairwise dissimilarity among n taxa (species). An old algorithm, known to biologists as UPGMA, is one way of producing such a tree. I will show that UPGMA is an algorithm that orthogonally projects the data point onto a distinguished cell of the space of all (equidistant) phylogenetic trees. This space is also known as the Bergman complex as well as the tropical variety of the matroid of the complete graph on n vertices. I will explain all these terms and show that "best" tree will be obtained by an orthogonal projection as well. This will lead us to an extended UPGMA algorithm.
Time: Friday, March 28, 2008, 3:30-4:20 p.m.Place: Science and Technology Building I, Room 242
Refreshments will be served before the talk at 3:00 p.m. in Room 222.
Department of Mathematical Sciences
George Mason University
4400 University Drive, MS 3F2
Fairfax, VA 22030-4444
http://math.gmu.edu/
Tel. 703-993-1460, Fax. 703-993-1491