The supposedly well-known carbonate indicator Tortella tortuosa (Pottiaceae, Bryophyta) split into eight species in Europe

We present a first treatment of the Tortella tortuosa complex for Europe. We analysed molecular relationships based on the nuclear ITS and the plastid atpB-rbcL and rps4 in a network context and thereafter characterized the identified entities by their morphology. We found eight morphologically and molecularly distinct entities at the species level, which are also supported in ASAP analyses of the molecular data; one species includes two varieties. In some cases, nuclear and plastid data suggest different relationships and we found a few likely recent hybrid collections. To the main characters of taxonomic importance belong stem anatomy, leaf shape and papillosity. We describe three species as new: T. commutata (a widespread plant; including the new var. valida), T. dolomitica (known only from the Alps) and T. splendida (an Arctic-alpine element), replacing T. arctica auct. For T. angustifolia and T. robusta (both montane) new combinations at the species level are provided. Tortella bambergeri (a submediterranean element), T. fleischeri (an Alpine element, recurring in Scotland) and T. tortuosa s. str. (widespread) complete this informal group of morphologically similar and partly related species. The species differ in ecological requirements and distribution areas, although mixed stands of two or three species are frequent. The area richest in species in Europe is the Alps with all eight species, whereas we found only four from Scandinavia.