Fig. 1.

Phylogenetic tree of the vascular plants, pruned for the 57 genera used in this study. The topology displayed was obtained from the maximally resolved seed plant tree available in Phylomatic (www.phylodiversity.net/phylomatic) and completed manually for fern species. For simplicity, branch lengths are not proportional to time since evolutionary divergence. The plot on the right side is the ΔLA score for each genus. The dotted line is the ΔLA = 0 reference line (i.e. the lowland and highland congeners have the same average leaf size).