Species delimitation and taxonomic revision of the Pyrrosia porosa complex (Polypodiaceae)

The Pyrrosia porosa complex represents one of the most taxonomically challenging lineages within Pyrrosia (Polypodiaceae). The number of recognized taxa within this complex has long been debated, with previous treatments accepting from one to 11 species. Widespread polyploidy and frequent hybridization have obscured morphological boundaries, resulting in continuous character variation within the complex and highlighting the need for a comprehensive taxonomic and systematic reassessment. To address these questions, we conducted a population-level study of species delimitation within the complex. We obtained morphological data from 282 specimens and 21 characters across 29 populations, and used multivariate and univariate analyses to identify diagnostic differences among putative taxa and delimit species boundaries. Moreover, we employed flow cytometry and spore size measurements to infer ploidy levels and detect potential hybridization. Ecological niche modelling was also performed to assess ecological differentiation among the recognized taxa. Integrating statistical morphological variations, and cytological and ecological evidence, we recognized eight taxa within the P. porosa complex, including seven diploid species (P. gralla, P. davidii, P. nudicaulis, P. stenophylla, P. tonkinensis, P. assimilis, and a newly described species, P. alpina) and one tetraploid species (P. porosa). Finally, a comprehensive taxonomic treatment is provided, including species descriptions and an identification key. Our results clarify species boundaries within the P. porosa complex and highlight the roles of polyploidy, hybridization, and ecological differentiation in fern speciation.