Fig. 4
Linear regressions between branch durations and branch weights for one phylogenetic tree. Plots in (a) were generated by calculating the branch weights using the “null” raster, whereas plots in (b) were generated by calculating the branch weights using the “elevation” raster treated as a resistance factor. Plots are shown for each of the three path models (straight line, least-cost, and random walk). The D value obtained under each path model is shown at the top. The plots show that the R2 of the regression is approximately doubled when spatial heterogeneity in elevation is taken into account