A taxonomic survey of terrestrial Orchidaceae from the northern coastal plain of Rio Grande do Sul was carried out. This region lies between the steep slopes of the Serra Geral and the Atlantic Ocean (29°10'S; 30°00'S). The study area has a moist subtropical Cfa-type climate. Mean annual temperatures vary from 17.5 to 20.0 °C, and precipitation varies from 1,200 to 1,700 mm. The natural vegetation is closely associated with small-scale topographic variation, which in turn affects soil drainage. It has been greatly reduced and modified by human activities. A total of 42 species belonging to 24 genera were identified based on the literature, herbarium specimens and extensive collecting throughout the study area. Two species are cited for the first time in Rio Grande do Sul. Many genera (17) were represented by a single species, while only one genus (Habenaria) had a relatively high number of species (8). Results include a new taxonomic combination, identification keys for genera and species, taxonomic and ecological observations, and citation of herbarium vouchers.
Orchidaceae; coastal vegetation; taxonomy; Rio Grande do Sul; Brazil
