Anatomy of leaf edges in Marantaceae in the Neotropics: the relationship between vernation and leaf asymmetry and contributions to the systematics of the family

Abstract

Abstract Marantaceae consist of species with asymmetric leaves of two types: those with either a wider left or right half; this asymmetry is related, respectively, to clockwise or counterclockwise convolute vernation. In this study, we analysed whether anatomical differences in the leaf edges, i.e. the anatomical asymmetry, were related to the orientation of the convolute vernation and to the asymmetry of leaf morphology, and whether these differences supported the organization of the clades in the family. Transverse sections of the mid third of the leaf buds expanded to the height of the right and left edges of the blades were prepared for 19 species belonging to 11 genera, using cyto-histological techniques. Anatomical analyses of the blade edges revealed that there is a relationship between morphological asymmetry and anatomical asymmetry that has never before been ascribed to the family. The anatomical data support differences between the arrangements in two of the three Neotropical informal groups. In the Calathea clade, Calathea showed much more similarity with Goeppertia than with Ischnosiphon and Monotagma, since they are the only genera that do not present with anatomical asymmetry. In the Maranta clade, Ctenanthe, Saranthe and Stromanthe appear to be related to one another, as they share strong anatomical asymmetry and fibrous edges. These characteristics, however, are not observed in Myrosma, which in turn is more anatomically similar to Maranta.