Abstract: This paper deals with the phylogenetic relationships in Sphagnum using the Wagner Groundplan-Divergence method. The main principle of the Wagner GPD method is grouping based on synapomorphy derived from outgroup comparison and ontogenetic analysis whenever possible. We make use of 21 available characters from gametophytes, estimate plesiomorphic conditions on the principle that characters found in the group under study and in most or all members of related groups are plesiomorphic, while those found only within the group are apomorphic, and finally arrange taxa according to shared derived features. In the Wagner tree diagrams, all characters can be placed on a Wagner tree so that the various relationships in the genus Sphagnum can be visualized. The results were as follows: 1. The genus Sphagnum can be divided into six sections, i.e. Sphagnum, Squarrosa, Acutifolia, Cuspidata, Subsecunda and Polyclada. They are almost consistent withe those derived from classical and numerical taxonomy of Sphagnum. 2. In Wagner tree diagrams, Section Sphagnum and Sect. Squarros were branched earlier, so they are primitive and the other four sections were last branched, so they are derived. Sphagnum magellanicum is a rather primitive species, whereus S. girgensohnii andS. fimbriatum are rather advanced ones in the 14 species of Sphagnum investigated.

Key words: Sphagnum, plesiomorphy, apomorphy, phylogenesis, Wagner GPD method