Adetogramma (Polypodiaceae), a new monotypic fern genus segregated from Polypodium

Polypodiaceae is one of the most diverse and abundant families of ferns in tropical and subtropical forests. Despite multiple studies investigating its phylogeny and taxonomy, several generic boundaries within the family still need clarification. One of the most problematic circumscriptions is that of Polypodium L., and one species that still contributes to this uncertainty is Polypodium chrysolepis Hook. The main goal of this study was to use molecular and morphological data to clarify the relationships of P. chrysolepis inside the polygrammoid clade. Sequences from three plastid regions (cpDNA - rbcL, rps4 and rps4-trnS IGS) from fifty species belonging to thirty-two genera of Polypodiaceae were analyzed using maximum likelihood and Bayesian inference. Polypodium chrysolepis constitutes an isolated lineage among the neotropical polygrammoid ferns, close to Serpocaulon and the grammitids, and is recognized here in a new genus. It can be distinguished by its entire leaves with free veins and peltate, pedicellate, lanceolate paraphyses. A new combination, Adetogramma chrysolepis, is proposed and a new taxonomic treatment is presented; its conservation status was assessed using IUCN Red List Categories and Criteria.