Hymenostylium chapadense M.J.Cano & J.A.Jiménez (Pottiaceae), a new species from Brazil and its phylogenetic position based on molecular data.

In the context of a taxonomic revision of the tribe Pleuroweisieae in South America, we studied a specimen of Hymenostylium that did not match any previously known species of this genus in America. Here we present our arguments for recognising this moss as a new species. The morphology of the potential new species was compared with that of the species of Hymenostylium presently recognised. A phylogenetic analysis based on the nuclear ITS and plastid rps4 regions was performed to investigate relationships between the new species and closely related taxa. Based on morphological and molecular data, we describe this new species from Brazil, Hymenostylium chapadense M.J.Cano & J.A.Jiménez. The species is strikingly distinguished by a stem with central strand and hyalodermis, oblong-ligulate to oblong-elliptical leaves that are when dry slightly crisped in the upper part and usually constricted just above the base and recurved on one side in the lower third, with uni- to bistratose margins, obtuse apex, costa wide and ending below the apex or percurrent with ventral and dorsal surface cells of the costa differentiated as an epidermis, and middle laminal cells usually with a simple, coarse, central papilla. Our molecular study placed H. chapadense as sister to H. hildebrandtii (Müll.Hal.) R.H.Zander. Possible confusion with the latter species and other closely related taxa is discussed. A key to the South American species of Hymenostylium is provided. [ABSTRACT FROM AUTHOR]