A taxonomic study of selected European taxa of the Tortula muralis (Pottiaceae, Musci) complex: variation in morphology and ploidy level.

Four European taxa of the Tortula muralis complex (T. lingulata, T. muralis var. aestiva, T. muralis var. muralis, T. obtusifolia) were evaluated using multivariate analysis of morphological characters, a cultivation experiment and cytological screening (flow cytometry, chromosome counts). This study revealed that only T. lingulata is morphologically well defined within the complex and several new sporophytic characters that can be used to distinguish this taxon from the superficially most similar T. obtusifolia. The traditionally recognized taxa T. muralis var. muralis, T. muralis var. aestiva and T. obtusifolia showed continuous variation, with frequent intermediate plants. However, the main character of the gametophyte used for determination (costa excurrency) proved to be stable in cultivation, indicating that this character is under genetic control. Additionally, rather complex and only partly species-specific patterns of ploidy variation were found within the complex. Tortula lingulata and T. obtusifolia appear to be cytologically homogeneous; plants of T. lingulata were found to be diploid, whereas plants tentatively named as T. obtusifolia were haploid. In contrast, both haploid and diploid cytotypes were found in both varieties of T. muralis, with a marked predominance of diploids in var. aestiva and less marked predominance of diploids in var. muralis. Current varietal level of the evaluated infraspecific taxa of T. muralis was thus found to be warranted. It is suggested that plants previously recognized as T. obtusifolia should be treated as a subspecies of T. muralis.