Reinstatement, redescription, and emending of Spiranthes triloba (Orchidaceae): solving a 118 year old cryptic puzzle

Spiranthes (Orchidaceae) is a primarily North American genus that has traditionally presented numerous taxonomic challenges. Many species display marked intra-species morphological variation and/or inter-species morphological similarities, such that cryptic speciation may be common. Molecular phylogenetic, morphological, field, and herbarium research concerning the delimitation of Spiranthes odorata necessitates the reinstatement and redescription of Spiranthes triloba, a name alternately synonymized under Spiranthes cernua and Spiranthes odorata for more than a century. While lost under synonymy, plants matching the morphology of Spiranthes triloba were ambiguously described as Spiranthes ×itchetuckneensis and Spiranthes ×folsomii, and these are here synonymized. Although the species has a descriptive specific epithet, the labellum of the holotype is decidedly not tri-lobed; Spiranthes triloba is redescribed and emended here so as to reflect its actual morphology. Spiranthes triloba is restricted to frequently burned calcareous prairies and flatwoods of Florida, and likely warrants protection at the state level. A key is provided to distinguish this species from other Spiranthes found in Florida, and a lectotype is designated for S. ×folsomii.