The genus Stelis Sw. (Orchidaceae) in Rio Grande do Sul, Brazil

Abstract

The genus Stelis Sw. comprises approximately 700 species occurring in rainforests of the Neotropics. Most species are epiphytic, with a caespitose habit, racemo inflorescence and small flowers with a triangular outline. The southern limit of the geographic distribution lies around 30ºS latitude in South Brazil. The objective of this study was to carry out a taxonomic study of the native species of Stelis in Rio Grande do Sul. Our study was based on botanical material deposited in regional herbaria, the citations of taxa in the scientific literature, and some field trips to collect new material. Based on morphological characters we presented an identification key for the species, and performed botanical descriptions and diagnostic illustrations of the indigenous species. We also compiled information on the geographical distribution, occurrence in different forest types and the flowering and fruiting seasons. Seven species of Stelis were confirmed for the State: S. aprica Lindl., S. deregularis Barb.Rodr., S. fraterna Lindl., S. intermedia Poepp. & Endl., S. megantha Barb.Rodr., S. papaquerensis Rchb.f. and S. pauciflora Lindl. Another set of seven species was excluded as former misidentifications, uncertain names or new generic circumscriptions. Most species of Stelis in Rio Grande do Sul are strongly associated to the southern limit of the Brazilian Atlantic Forest, and so they are more commonly found or even restricted to the northeast part of the State.