Morphological and Molecular Evidence to Segregate a Disjunct Species of Hymenophyllum (Hymenophyllaceae) from Southern South America

—Morphological studies and molecular phylogenetic analyses were carried out to assess the taxonomic status of Hymenophyllum caudiculatum, a species with a disjunct distribution in South America. The species is found in tropical and subtropical forests of Brazil and in temperate forest of southern Argentina and Chile. Based on the results of morphological, molecular, and species delimitation analyses, Hymenophyllum caudatum of the Valdivian forest of southern Chile and Argentina is proposed as a species separate from H. caudiculatum, endemic to Brazil. The two taxa are delimited, respectively, as follows: 1‐5 cm long non-alate stipes (vs. 0.3‐1 cm long non-alate stipes in Brazilian H. caudiculatum); stipe wings gradually ending (vs. stipe wings abruptly ending very near the rhizome); margin entire to somewhat undulate (vs. margin undulate to crispate); soriferous segment alate, angustate, or null (vs. soriferous segment with laminar constriction at apex); and widely obovoid receptacle with sessile sporangia (vs. flattened obovoid or globose receptacle with shortly pedunculated sporangia). Descriptions for the two species recognized here and a map of their geographical distribution are provided, along with nomenclatural revision, illustrations, and conservation status assessments.