Phylogenetics and systematics of selligueoid ferns based on comprehensive taxon sampling and a phyloplastomic backbone

Abstract The selligueoid ferns are a diverse group of epiphytes comprising more than 100 species. Their substantial disparity in frond morphology has led to the recognition of more than 16 genera with the dominant ones including Arthromeris , Crypsinus , Gymnogrammitis , Phymatopteris , Polypodiopteris , and Selliguea . In this study, we sampled 150 collections representing 69 species and compiled two plastid datasets. One dataset includes six plastid regions of all 69 species, and the other includes the plastomes of 19 representatives of major lineages. Phylogenetic analyses identified four strongly supported clades within the selligueoids and clarified the composition of each. Dating and historical biogeography analyses suggest that the genus Selliguea diverged around 26–34 million years ago, with its origin traced to Asia. The evolution of six morphological characters was also reconstructed on the phylogeny. We recognize the selligueoids in a broad sense and further classify them into four subgenera: Selliguea subg. Arthromeris , subg. Hastata , subg. Pichisermollodes , and subg. Selliguea . Furthermore, we found that their plastomic structures are phylogenetically informative. We identified two major expansions and one significant contraction of the inverted repeat (IR) region in the selligueoids. One of these expansions led to an inverted repeat that encompassed all the genes of the small single‐copy region (SSC), which resulted in SSC regions lacking genes and with sizes dramatically reduced to less than 100 bp in S. subg. Hastata . Subsequently, one IR contraction occurred in the common ancestor of the derived lineages within S. subg. Hastata .