Himalayan or tropical Asian origin: New insights into the phylogeny, biogeography, and systematics of the fern genus Selliguea and its allied genera (Polypodiaceae)

Abstract Selligueoid ferns are arguably one of the only relatively large groups of ferns with uncertain phylogeny, biogeography, and systematics. Previous studies identified some well‐supported or moderately supported clades but their relationships were largely unresolved, and thus, it remains controversial whether these ferns originated from tropical Asia or the Himalaya and how many genera should be recognized. Here, we reconstructed phylogenies based on Sanger sequencing data of five plastid markers of 261 accessions representing ca. 103 species and 67 (49 ingroup) plastomes representing 41 species of selligueoids and 18 species of outgroups. Our data resolved selligueoids into six major clades and recovered the monophyly of Arthromeris , Pichisermollodes , and Phymatopteris (excl. type) + Gymnogrammitis , whereas Selliguea will become monophyletic if two isolated species are excluded. Contrasting lumping all genera into one genus, here, we propose to recognize six genera: Arthromeris , Phymatopteris , Pichisermollodes , Selliguea , Coumariphylla (four spp.), and Vietiglossa (one sp.), in addition to the hybrid genus, × Phymatomeris . We support the proposal to conserve Phymatopteris with a new type. Phymatopteris and Selliguea are found not to co‐occur in any locality. Our results suggested that selligueoids originated in the late Eocene (ca. 36.4 Mya) in the Malesia–Pacific area, consistent with the tropical Asian origin hypothesis. Quite surprisingly, only two long‐distance dispersals and local range expansions/diversifications contributed to the current distribution pattern of selligueoid ferns. In support of our classification, we provide a key to the six genera, their morphological and geographical synopses, and lists of their constituent species and important synonyms.