Phylogeny of Digitaria Sections Trichachne and Trichophorae (Poaceae, Panicoideae, Paniceae): A Morphological and Molecular Analysis. New Circumscription and Synopsis

Abstract

The present study provides evidence for taxonomic delimitation of Digitaria sect. Trichachne based on morphological data (micro- and macromorphology) and molecular data. A phylogenetic analysis was performed using 121 morphological characters and ITS sequences of 22 species and one variety of Digitaria plus three outgroups. In all topologies (based on morphological, molecular, and combined data) Digitaria sect. Trichophorae was non-monophyletic and nested within D. sect. Trichachne. Digitaria sect. Trichophorae is thus synonymized under D. sect. Trichachne and the circumscription of D. sect. Trichachne is emended. Diagnostic morphological characters related to spikelet structure are described and documented with SEM. A key to taxa belonging to D. sect. Trichachne is provided, as well as a synopsis including synonymy, iconography, geographical distribution, and ecology. The neotype of Trichachne sacchariflora Nees is herein designated. Complete illustrations of Digitaria eggersii, D. hitchcockii, and D. patens are provided. The phylogenetic placement of the Australian species D. brownii differed among trees resulting from different data sets, thus it is provisionally not included in D. sect. Trichachne in spite of its morphological similarity. Furthermore, Megaloprotachne albescens is formally transferred to Digitaria, as Digitaria albescens.