Relevance of leaflet morphoanatomical characters in the taxonomy and ecology of seven species of the genus Mimosa (Leguminosae, Caesalpinioideae, Mimoseae)

The genus Mimosa is complex; it is distributed in a wide variety of habitats, and the delimitation of several of its species remains problematic. To date, leaflet morphoanatomy has not been explored in most of its species, despite the fact that such exploration would not only make it possible for the species to be distinguished but also provide information about the environment. It was for these reasons that the taxonomical and ecological implications of the morphoanatomical characters of seven Mimosa species’ leaflets were determined. The architecture and anatomy of three leaflets were observed in three individuals per species. Interspecific differences were evaluated through analysis of variance. Similarity analysis and a non-metric multidimensional scaling analysis were performed. Traits showed associations with several environmental variables using canonical correspondence analysis. The characters with specific taxonomic value include primary venation type, stomatal complex type, mesophyll type, presence or absence of twice-branched veinlets, and cuticular folds over the primary vein. The analysis of similarities grouped the species according to the section to which they belong (M. sect. Batocaulon, M. sect. Habbasia, and M. sect. Mimosa). Furthermore, the characters are associated with protection against solar radiation, reduction of water loss, and optimization of water transport and photosynthesis. This study demonstrates that leaflet morphoanatomical characters are important for the resolution of taxonomic problems and can provide insight into the survival strategies employed by Mimosa species, thus pointing the way for future exploration of the topic.