Wagner S. T. auteur aut IRD Hesse L. auteur aut IRD Isnard Sandrine auteur aut IRD Samain M. S. auteur aut IRD Bolin J. auteur aut IRD Maass E. auteur aut IRD Neinhuis C. auteur aut IRD Rowe N. P. auteur aut IRD Wanke S. auteur aut IRD text journalArticle eng text/pdf born digital access Background and Aims The order Piperales has the highest diversity of growth forms among the earliest angiosperm lineages, including trees, shrubs, climbers and herbs. However, within the perianth-bearing Piperales (Asarum, Saruma, Lactoris, Hydnora, Prosopanche, Thottea and Aristolochia), climbing species only occur in the most species-rich genus Aristolochia. This study traces anatomical and morphological traits among these lineages, to detect trends in growth form evolution and developmental processes. Methods Transverse stem sections of different developmental stages of representatives of Asarum, Saruma, Lactoris, Hydnora, Thottea and Aristolochia were compared and anatomical traits were linked to growth form evolution. Biomechanical properties of representative climbers were determined in three-point bending tests and are discussed based on the anatomical observations. Growth form evolution of the perianth-bearing Piperales was reconstructed by ancestral character state reconstruction using MESQUITE. Key Results While species of Asarum and Saruma are exclusively herbaceous, species of the remaining genera show a higher diversity of growth habit and anatomy. This growth form diversity is accompanied by a more complex stem anatomy and appropriate biomechanical properties. The ancestral growth form of the perianth-bearing Piperales is reconstructed with either a shrub-like or herbaceous character state, while the following three backbone nodes in the reconstruction show a shrub-like character state. Accordingly, the climbing habit most probably evolved in the ancestor of Aristolochia. Conclusions Since the ancestor of the perianth-bearing Piperales has been reconstructed with a herb-or shrub-like habit, it is proposed that the climbing habit is a derived growth form, which evolved with the diversification of Aristolochia, and might have been a key feature for its diversification. Observed anatomical synapomorphies, such as the perivascular fibres in Lactoris, Thottea and Aristolochia, support the phylogenetic relationship of several lineages within the perianth-bearing Piperales. In addition, the hypothesis that the vegetative organs of the holoparasitic Hydnoraceae are most probably rhizomes is confirmed. specialized Aristolochia Thottea Lactoris Hydnora Asarum Saruma growth form anatomy biomechanics secondary woodiness heterochrony perianth-bearing Piperales 076 113 7 1139-1154 2014 0305-7364 https://www.documentation.ird.fr/hor/fdi:010062261 10.1093/aob/mcu044 0305-7364 [F B010062261] https://www.documentation.ird.fr/hor/fdi:010062261 https://www.documentation.ird.fr/intranet/publi/2014/07/010062261.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2014-07-24 2017-08-23 fdi:010062261 fre