A new species of Merostachys (Poaceae: Bambusoideae: Bambuseae: Arthrostylidiinae) with the northernmost distribution of the genus

With 52 described species, Merostachys is the most diverse genus in the Arthrostylidiinae; 50 of the species are present in South America and only two, M. latifolia and M. pauciflora, are distributed in Central America and Mexico. Previous collections of vegetative Merostachys specimens from El Triunfo, Chiapas, Mexico, were identified as M. pauciflora. However, new flowering collections from the state of Tabasco, Mexico, allowed us to differentiate the Mexican populations from M. latifolia and M. pauciflora. A detailed study of samples from the Tabasco population, and a review of the previous collections from Chiapas, confirmed the existence of a new Merostachys species, which we here describe and illustrate as M. mexicana. This new species is endemic to Mexico and represents the northernmost extension of the genus.