Abstract
A taxonomic study of the Hymenasplenium unilaterale subclade (Aspleniaceae) is presented based on morphological and molecular evidence. Twelve species are recognized, nine of which are described as new. The nine new species include H. kinabaluense, H. solomonense, H. madagascariense, H. nigricostatum, H. neocaledonicum, H. oligosorum, H. queenslandicum, H. samoaense, and H. vanuatuense. Of the 12 species recognized, one occurs in Malaysia, East Africa, and Reunion, one in southern Vietnam, and the rest restricted to 1–2 islands of the Indian Ocean or the Pacific Ocean. These new species have been erroneously treated as H. unilaterale by earlier pteridologists. All species were included in a recent phylogenetic analysis and supported as distinct lineages based on molecular data. A key to the species and information on their distributions, habitats, and major distinguishing characters are provided.