New contributions of comparative leaf anatomy to the phylogeny of Stigmaphylloids (Malpighiaceae Juss.)

Abstract

In the most recent Malpighiaceae phylogeny, Bronwenia and Diplopterys emerge segregated from Banisteriopsis and closely related to Stigmaphyllon, all forming an unresolved clade in the family. Here, we investigate anatomical characters that distinguish the genera Bronwenia and Diplopterys, using Stigmaphyllon and Banisteriopsis as outgroups, to support the phylogenetic relations in the Stigmaphylloid clade and subside classifications based on leaf anatomy in future studies. With this purpose, we evaluated the leaf anatomy of these four genera using traditional anatomical techniques and reconstructed promising characters using the molecular phylogeny of Malpighiaceae. Characters like petiole and primary venation contour, accessory bundles, leaf trichomes, leaf druses, mesophyll organization, leaf sheath extension, internal glands and prismatic crystals are informative due to their taxonomic value in Stigmaphylloids. The organization of the petiole vascular system allows the distinction of genera segregated from Banisteriopsis. Besides, the non-continuous bi-stratified adaxial epidermis of the leaf blade is relevant to the distinction of species of Bronwenia. However, the variation of this character in Diplopterys makes it useful only at the genus level. Mapping the anatomical characters in the phylogenetic tree can help ground new infra and suprageneric classification proposals.