THE ORIGIN OF LAND PLANTS - PHYLOGENETIC-RELATIONSHIPS AMONG CHAROPHYTES, BRYOPHYTES, AND VASCULAR PLANTS INFERRED FROM COMPLETE SMALL-SUBUNIT RIBOSOMAL-RNA GENE-SEQUENCES

Complete nuclear-encoded small-subunit 18S rRNA (=SSU rRNA) gene seque nces were determined for the prasinophyte green alga Mantoniella squam ata; the charophycean green algae Chara foetida, Coleochaete scutata, Klebsormidium flaccidum, and Mougeotia scalaris; the bryophytes Marcha ntia polymorpha, Fossombronia pusilla, and Funaria hygrometrica; and t he lycopod Selaginella galleottii to get a better insight into the seq uential evolution from green algae to land plants. The sequences were aligned with several previously published SSU rRNA sequences from chlo rophytic and charophytic algae as well as from land plants to infer th e evolutionary relationships for major evolutionary lineages within th e Chlorobionta by distance matrix, maximum parsimony, and maximum like lihood analyses. Phylogenetic trees created by the different methods c onsistently placed the Charophyceae on the branch leading to the land plants. The Charophyceae were shown to be polyphyletic with the Charal es (''charalean'' algae) diverging earlier than the Coleochaetales, Kl ebsormidiales, Chlorokybales, and Zygnematales (''charophycean'' algae ) which branch from a point closer to the land plants in most analyses . Maximum parsimony and maximum likelihood analyses imply a successive evolution from ''charophycean'' algae, particularly Coleochaetales, t o bryophytes, lycopods, and seed plants. In contrast, distance matrix methods group the bryophytes together with the ''charophycean'' algae, suggesting a separate evolution of these organisms compared with the club moss and the seed plants.