Leaf structure in Amorimia and closely related Neotropical genera and implications for their systematics and leaf evolution in Malpighiaceae

Abstract

AbstractAmorimia (Malpighiaceae) was recently segregated from the polyphyletic Mascagnia and placed in the malpighioid clade; identifying new characters based on leaf structure is among the first steps towards a proper generic delimitation of these segregates of Mascagnia. A comprehensive study describing and testing the relevance of leaf-structure characters in the evolution of Amorimia and related Neotropical genera is presented. We sampled all 15 Amorimia spp. and, as outgroups, eight species from the closely related Neotropical genera (Diplopterys, Ectopopterys, Mascagnia, Peixotoa and Stigmaphyllon). We scored 85 structural characters and mapped them on the most recent phylogenetic tree recovered for the genera. The presence of druses in the palisade parenchyma, the position of fibres alongside the vascular bundle and the occurrence of fibre blocks near the margin of the leaf blade were recovered as anatomical synapomorphies for Amorimia. Our results are a first step towards recovering anatomical and macromorphological synapomorphies for newly identified lineages of Malpighiaceae, such as Amorimia.