Abstract
In the course of a worldwide revision of the genus Syntrichia, we identified problems in the circumscription of some species of the genus as well as among some allied genera grouped in the tribe Syntricheae. This is the case for the two propagulose Syntrichia amphidiacea and S. gemmascens, closely related to Streptopogon. We analyzed phylogenetic relationships between these species, based on nuclear (ITS) and two plastid (trnL-F and trnG) markers and morphological features. Species delimitation using molecular data was consistent with our preliminary morphological inference. Phylogenetic analyses were performed using maximum likelihood and Bayesian inference methods. Our results placed Syntrichia amphidiacea in the Streptopogon clade. Syntrichia gemmascens is also included in Streptopogon in spite of the discrepancy of the ITS and plastid relationships, which could be evidence of an exchange of genetic material between species in various lineages in the Pottioideae. Streptopogon is maintained as a separate genus on the basis of morphology characters, and we consider the differentiation of laminal papillae and the presence of a stem central strand as new characters in the genus. We accept Sagenotortula as distinct genus sister to Syntrichia. We consider the lack of costal dorsal epidermis and the differentiation of a crescent-shaped costal dorsal stereid band as distinctive generic characters in Syntrichia. Additionally, we include Syntrichia percarnosa as a new synonym for S. breviseta. Three names are lectotypified.