Phylogeny of the Characeae (charophyta) inferred from organismal and molecular characters

Abstract

Phylogenetic hypotheses proposed for extant genera of the Characeae by Wood & Imahori (1965) and by Khan & Sarma (1984) are based on morphological characters, and morphological characters and chromosome numbers respectively. For all six extant taxa, cladistic analyses have been performed on organismal characters and chromosome numbers, sequence data from the nucelar-encoded small subunit rRNA gene, and a combined morphological and molecular data set. These analyses support: 1) monophyly of the Characeae, 2) monophyly of tribe Chareae, 3) placement of Nitellopsis basal to the rest of the Chareae, and 4) monophyly of Lamprothamnium. Neither the Wood & Imahori nor the Khan & Sarma hypothesis is strongly supported. Additional analyses based on a more comprehensive taxon sampling may help resolve: 1) monophyly of Chara, 2) monophyly of Nitella, 3) monophyly of the Nitelleae, 4) placement of Nitella axillaris, and 5) placement of Lamprothamnium.