Leaf size and shape in the Sphagnum recurvum complex: taxonomic significance and habitat variation

Six leaf size and shape characters from branch and stem leaves of five morphs in the Sphagnum recurvum complex were investigated at 154 mire microsites. Eighty-six of the collections included mixed stands of two or more morphs. The different morphs were distinguished in the field using capitulum appearance and characteristics. The microsites were classified according to "wetness" and "nutrient-richness" level- s. The factor "morph" accounted for the major part of the variation in the variables: breadth:length ratio of branch and stem leaves, length and breadth of branch leaves and length of stem leaves. Wetness was the factor accounting for most of the variation in breadth of stem leaves. Sphagnum angustifolium from mixed stands was well differentiated from the other species regarding leaf characters, while the differences in breadth and length of stem leaves of the closely related taxa S. fallax and S. isoviitae seemed to depend on nutrient status in the habitat where the mixed stands were collected. The present study shows that leaf size and shape characters can provide valuable aid for the separation of morphs within the complex. It also implies that knowledge of morphological behaviour over a range of habitats is necessary to fully understand the va riation in characters between the morphs in the complex.