Hidden and neglected taxa inside a collective taxon: taxonomic revision of Woodsiaceae in the Southern Cone of South America

Woodsiaceae is a monophyletic fern family comprising around 65 taxa that inhabit mainly mountainous areas of the northern hemisphere but also with numerous species in southern America and Africa. Recent molecular studies recognize two genera in the family: Woodsia, restricted to the northern hemisphere, and Physematium, present in Central and South America, Africa and East Asia. Traditionally, in South America the family has been considered to include a single species, Woodsia montevidensis, very variable morphologically, a treatment that underestimates the diversity of South American taxa. Therefore, we carried out a taxonomic review that included comparative analyses of morphological and palynological characters as well as distributional data. In the Southern Cone, Physematium is characterized by sori with saucer- or bowl-shaped lower indusia, splitting into 1–3 lobes in the mature sori. The taxa inhabit mountainous regions, between 200 m to more than 4000 m in altitude. Four species are recognized in the genus Physematium in the Southern Cone: one new species, P. hieronymi, and three that were previously treated as synonyms of P. montevidense, publishing here the corresponding new combinations. A key, descriptions, illustrations and distribution maps of the species are provided. Citation: Ponce M. M., Gorrer D. A. & Arana M. D. 2025: Hidden and neglected taxa inside a collective taxon: taxonomic revision of Woodsiaceae in the Southern Cone of South America. – Willdenowia 55: 29–49. Version of record first published online on 20 March 2025.