Diversity of silica bodies in Mourera Aublet (Podostemaceae) and its phylogenetic, paleobotanical, and taxonomic applications

Abstract

We tested the phylogenetic, paleobotanical, and taxonomic (i.e., presence, location, and morphology) relevance of silica bodies in leaves of Mourera (M. aspera, M. elegans, M. fluviatilis, M. glazioviana, M. schwackeana, and M. weddelliana). Leaf samples were macerated and examined using light and scanning electron microscopy. The location of silica bodies was determined through cross- and longitudinal–anatomical sections. Silica bodies were found in all analyzed species of Mourera, occurring in the subepidermal cells and/or in the perivascular cells. These structures presented different shapes in each analyzed species, being noteworthy the presence of polygonal and trapeziform shapes in M. fluviatilis, bifid shape in M. aspera and M. weddelliana, and fusiform shape in M. elegans and M. schwackeana. Three ornamentation types were recognized: verrucate, verrucate–granulate, and verrucate–nodulate. The width/length ratio ranged from 34 (M. elegans) to 60.8% (M. fluviatilis). The location and morphology of silica bodies allowed the identification at the species level. Our results emphasize the relevance of these character states on a forthcoming phylogenetic analysis and taxonomic revision of Mourera, as well as in its recognition in paleo-sedimentary environments.