Stem anatomy and growth forms in perianth-bearing Piperales

The order Piperales has the highest diversity of growth forms among the earliest angiosperm lineages, including trees, shrubs, climbers and herbs. Wagner et al. trace anatomical and morphological traits among the perianth-bearing Piperales in order to detect trends in growth form evolution and developmental processes, and show that growth form divergence is accompanied by changes in stem anatomy and appropriate biomechanical properties. They propose that the highly specialized climbing habit is a derived form that evolved with the diversification of Aristolochia, and might have been a key feature for the diversification of this genus.