Morphological and molecular data reveal a new spider species of the little-known Pholcus nagasakiensis species group (Araneae, Pholcidae) from the Ryukyu Archipelago

The Pholcus nagasakiensis species group is a relatively small group, comprising only five species. Of these, four species inhabit Kyushu Island in mainland Japan, the Ryukyu Archipelago and the Diaoyu Islands of China, while one additional species has been documented from Wuyishan Mountain in mainland China.Three morphologically similar species from the Ryukyu Archipelago, belonging to the Pholcus nagasakiensis species group were identified, based on an integrative approach combining morphology and molecular species-delimitation methods. These comprise one new species, namely Pholcus yajiyagama Yan, Ballarin & Yao, sp. nov., herein described, based on both sexes and two previously described species, P. nagasakiensis Strand, 1918 and P. otomi Huber, 2011. DNA barcodes were obtained for all three species to estimate p-distances and K2P distances and confirm their identifications. New diagnoses and detailed photomicroscopy images of the two previously described species, as well as a distribution map of all the species discussed, are also provided.