Insights into the systematics of Old World taenitidoid ferns (Pteridoideae; Pteridaceae): evidence from phylogeny and micromorphology

A close relationship of the three Old World taenitidoid genera Austrogramme, Syngramma and Taenitis was traditionally suggested on the basis of morphology, and later gained further support from molecular phylogenetic analyses. However, due to insufficient sampling, the monophyly and intrageneric and interspecific relationships of these genera are still largely untested, and the systematic value of diagnostic morphological characteristics is unclear. In this study, we generated a molecular phylogenetic tree with 18 species representing nearly half of the known species diversity for this group. In addition to macromorphological characteristics, we also observed microscopic characteristics, including soral paraphyses and spores. Our results confirm the monophyly of the three genera and their delimitating characteristics. We found that most of the previously proposed sections are not monophyletic, and their diagnostic characteristics are homoplastic. We propose new hypotheses concerning both intergeneric and interspecific hybridization and provide new taxonomic insights that are critical in understanding the diversity of the group.