Abstract
The nuclear-encoded small subunit ribosomal RNA (rRNA) sequences were determined for Genicularia spirotaenia, Mesotaenium caldariorum, and Staurastrum spec. (Zygnematales) to elucidate the evolutionary position of these green algae. Results of neighbour-joining and maximum parsimony phylogenetic analyses support a monophyletic origin of the Zygnematales within the evolutionary assemblage defined by the Charophyceae (sensu Mattox & Stewart) and land plants. The Zygnematales/Charophyceae/land plants are evolutionarily distinct from the monophyletic lineage defined by the Chlorodendrales, Pseudoscourfieldiales, and the Microthamniales/Chlorophyceae.