New data on the systematics of the European-Asian species of Leucodon (Leucodontaceae, Bryophyta)

Abstract

The European Leucodon species, L. immersus, L. flagellaris and L. pendulus, as well the Asian L. coreensis were studied and compared with the widely distributed L. sciuroides in light of DNA sequences and morphometric data. The study focused mainly on Eastern Europe and Western Asian specimens. The nrITS spacers were sequenced and 17 morphological characters were statistically analyzed. The Bayesian analysis of the molecular data showed that L. pendulus is sister to the remaining members of the Leucodon clade. The species L. coreensis, L. flagellaris, L. immersus and L. sciuroides were very closely related and their relationships were poorly resolved by the sequence data. Only L. coreensis showed a certain genetic distance from the other members of the clade but did not receive a solid support value. The nrITS DNA sequences offer no help in delimitating L. flagellaris and L. immersus. The differences between L. immersus and L. sciuroides shared by all specimens included in this study were two mutations in the alignment. No sequence differences separated L. sciuroides var. morensis from L. sciuroides var. sciuroides and only phyllidia size and alar region length were greater than in L. sciuroides var. sciuroides. We agree with the previous synonymization of both taxa. The best character for distinguishing L. flagellaris and L. pendulus was confirmed to be the central strand, as both species have pendent circinate flagelliform shoots and their lengths overlap. L. flagellaris and L. immersus can be clearly differentiated not only by the presence of pendent flagelliform shoots in the former but also by the phyllidia size, which are bigger in L. immersus than in L. flagellaris. L. immersus and L. sciuroides can be confidently separated by the short seta and the immerse capsule of the former; furthermore, L. immersus all measured gametophytic characters were statistically bigger than in L. sciuroides but individual plants cannot be reliably identified based on this because the value-range is overlapping. Morphologically L. coreensis and L. sciuroides can only be differentiated by the central strand, which is absent or illdefined in the former and well defined in the latter, while the alar region length was not statistically significant, as a distinguishing character as previously stated by other authors.