Spiranthinae (Orchidaceae - Cranichideae) from Uruguay: taxonomy and distribution

ABSTRACT Uruguay occupies an area of special relevance for species of terrestrial orchids of the subtribe Spiranthinae because it is located in one of the largest continuous grassland regions of the Americas. The aim of this study is to provide a taxonomic study of Spiranthinae species from Uruguay. A total of 22 species distributed in seven genera were confirmed to the country, representing almost half of the species of terrestrial orchids in Uruguay. Cyclopogon (8 spp.), Skeptrostachys (5 spp.) and Brachystele (4 spp.) were the most representative. Additionally, a new synonym in Brachystele dilatata (=Brachystele waldemarii) is proposed. The group was found in all departments and ecoregions of the country, mainly in the southeastern (Maldonado: 10 spp., Rocha: 12 spp. Lavalleja: 10 spp.) and northeastern (Rivera: 11 spp., Tacuarembó 9 spp.) regions. Among the ecoregions, the “Serrano Forest” (17 spp.) and “Graben de la Laguna Merín” (14 spp.) were the most species-rich. Descriptions, illustrations, an identification key, and comments on geographical distribution of the species are provided.