  Shortest paths in treespace, which represent minimal deformations between
trees, are unique and can be computed in polynomial time. The ability to
quickly compute shortest paths has enabled new approaches for statistical
analysis of populations of trees and phylogenetic inference. This paper gives a
new algorithm for updating geodesic paths when the end points are dynamic. Such
algorithms will be especially useful when optimizing for objectives that are
functions of distances from a search point to other points e.g. for finding a
tree which has the minimum average distance to a collection of trees. Our
method for updating treespace shortest paths is based on parametric sensitivity
analysis of the maximum flow subproblems that are optimized when solving for a
treespace geodesic.
