Extracts the time from root of each node in an
hansentree formatted phylogenetic tree; used to compute the timing of regime shifts in a Hansen model
A vector of branching times
Ingram, T. & Mahler, D.L. (2013) SURFACE: detecting convergent evolution from comparative data by fitting Ornstein-Uhlenbeck models with stepwise AIC. Methods in Ecology and Evolution 4: 416-425.