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SUMMARY:The combinatorics of distance-based tree inference - Pardi\, F (CN
 RS)
DTSTART:20110624T094000Z
DTEND:20110624T100000Z
UID:TALK31880@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Several popular methods for phylogenetic inference (or hierarc
 hical clustering) are based on a matrix of pairwise distances between taxa
  (or any kind of objects): the objective is to construct a tree with branc
 h lengths so that the distances between the leaves in that tree are as clo
 se as possible to the input distances. If we hold the structure (topology)
  of the tree fixed\, in some relevant cases the optimal values for the bra
 nch lengths can be expressed using simple combinatiorial formulae. Here we
  define a general form for these formulae and show that they all have two 
 desirable properties: first\, the common tree reconstruction approaches (l
 east squares\, minimum evolution)\, when used in combination with these fo
 rmulae\, are guaranteed to infer the correct tree when given enough data (
 consistency)\; second\, the branch lengths of all the simple (NNI) rearran
 gements of a tree can be calculated\, optimally\, in quadratric time in th
 e size of the tree. The study presented here may form the basis for novel 
 effcient search algorithms for distance-based tree reconstruction.\n
LOCATION:Seminar Room 1\, Newton Institute
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