Leaf epidermal characteristics of Lotus subgenus Acmispon (Fabaceae: Loteae) and a numerical taxonomic evaluation

Abstract

This paper describes the leaf epidermal characteristics of the New World species of Lotus L. subgenus Acmispon Raf. (Fabaceae: Loteae), computes their phenetic relationships based on morphological and anatomical characters, and compares these results with previous classifications and a recent phylogenetic hypothesis for the group based on morphological data. Leaves of 16 species of Acmispon were cleared and examined using light microscopy. Data on epidermal cells, stomata, stomatal index, and trichomes were described and summarized. To test the taxonomic value of epidermal characters and to ascertain phenetic relationships, we performed two numerical analyses using unweighted pair-group arithmetic average clustering. Results of the numerical analysis (16 operational taxonomic units (OTUs) × 13 epidermal characters) suggested that epidermal characteristics are insufficient to resolve sections Simpeteria and Microlotus. An additional analysis (16 OTUs × 23 characters) demonstrated that epidermal micro morphological features, together with other characters, are useful and informative for distinguishing these two sections. Results generated by the latter analysis accord well with earlier classifications and a previous phylogenetic hypothesis by showing that the sections Simpeteria and Microlotus are coincident with the two monophyletic subgroups Grandiflorus and Salsuginosus, respectively, inferred using cladistic analysis.Key words: Acmispon, epidermis, Fabaceae, Loteae, Lotus, Microlotus, Simpeteria.