Figure 1.

Cladogram showing phylogenetic relationships within Apocynaceae and key floral and seed morphological innovations, along with information on growth form, number of species, and evolution of the pollination system. Woody species are trees, shrubs, and/or lianas, black = presence, grey = absence. (A, B) Rauvolfioid versus APSA flower. Light gray = stamens; dark gray = style head. (A) Rauvolfioid flower with stamens free from style head; (B) APSA flower with gynostegium (anthers attached to style head). (C–F) Evolution of pollen aggregation and two morphologically distinct bauplans for translators composed of style‐head secretions and pollinaria (translator + pollinia) in Periplocoideae (C, D), Secamonoideae (E) and Asclepiadoideae (F). White = adhesive; light gray = pollen; dark gray = translator. (C) Side view of a firm scoop‐like translator with sticky adhesive lining by which the pollen (aggregated into porate tetrads) adhere to the scoop and with a sticky disc (viscidium) at the base of the translator to attach the translator to the pollinator. (D) Front view of pollinarium formed of a translator with adhesive‐lined scoop onto which porate pollen tetrads (aggregated into pollinia without a pollen wall) are shed, and with viscidium at the base. (E) Pollinarium comprising a translator with four sessile pollinia composed of inaperturate tetrads without a pollinium wall, attaching to the pollinator via a clip mechanism. (F) Pollinarium comprising a clip‐type translator and two pollinia composed of single inaperturate pollen grains with a pollinium wall and attached to the clip by arms. Additional potential drivers of diversification following Bitencourt et al. (2021): 1 = dry fruit with comose seeds, 2 = climbing habit. Tribes behind grey branches = rauvolfioids, blue = apocynoids, green = Periplocoideae, yellow = Secamonoideae, and red = Asclepiadoideae. Relationships after Fishbein et al. (2018) using the plastid phylogeny under constraint of the plastome, with updated relationships of Echiteae and sister clades based on Morales et al. (2017)—except for the position of Rhabdadenieae. Number of species per taxon and specifics on woody growth form type based on Endress et al. (2019). Botanical illustrations 1, 2, A, and B made by Esmée Winkel, C–F drawn and adapted from Endress (2003). Illustrations are not to scale.