Targeted sampling in Ryukyus facilitates species delimitation of the primitively segmented spider genus Ryuthela (Araneae: Mesothelae: Liphistiidae)

Molecular-based species delimitation approaches greatly facilitate discovering species in taxa with considerable intraspecific morphological variation, in those lacking diagnostic morphological characters or in those rare in collections. A combination of molecular species delimitation and morphological diagnosis has recently helped resolve parts of species diversity in primitively segmented spiders (family Liphistiidae), in which female genitalia are highly variable and thus difficult to diagnose, and males are often unknown. Here, we provide a taxonomic revision of the liphistiid genus Ryuthela Haupt, 1983, endemic to Ryukyu archipelago, Japan, through a combination of molecular and morphological data in a phylogenetic framework. We barcoded 173 originally collected specimens of 15 putative species using the universal cytochrome c oxidase subunit I (COI) mitochondrial marker and used these data for species delimitation estimates. The analytical approaches involved two genetic variation-based methods (DNA barcoding gap and automatic barcode gap discovery) and two tree-based methods [species delimitation plugin (P ID(Liberal)) and generalized mixed Yule-coalescent model (GMYC)]. All species delimitation methods except for GMYC suggest that Ryuthela consists of the five currently deemed valid species plus one named and as many as nine newly discovered species. Our findings shed light on species diversity of endemic spiders in one of the Asian biodiversity hotspots, and a formal taxonomy of 15 species completes the genus revision.