Arachniodes × tohtomiensis hyb. nov. (Dryopteridaceae) from Japan

This study aims to characterize a hybrid of <i>Arachniodes</i> (Dryopteridaceae), <i>A. × tohtomiensis</i>, for which molecular evidence of its origin and detailed morphological descriptions are lacking. The genome composition of <i>A. × tohtomiensis</i>, clarified based on plastid DNA and MIG-seq analyses, indicates that it is a diploid hybrid of <i>A. exilis</i> and an undetected species. This origin was also supported by phylogenetic, STRUCTURE, principal component, and neighbor-net analyses. Based on these evidences, it is formally described as <i>A. × tohtomiensis</i> Shimura & Hori, <b>hyb. nov</b>. It is morphologically characterized by its yellowish-green laminae and erose-to-ciliate indusia.