Polygamous breeding system identified in the distylous genus Psychotria: P. manillensis in the Ryukyu archipelago, Japan

Distyly is a genetic polymorphism composed of long-and short-styled flowers in a population. The evolutionary breakdown of distyly has been reported in many taxa, and mainly involves a shift toward monomorphism or dioecism. However, a shift toward monoecism has not been reported in distylous species. Psychotria (Rubiaceae), one of the world largest genera, consists of distylous species and their derivatives. In our preliminary study, however, we identified some monoecious individuals in a population of Psychotria manillensis. To understand the breeding system and reproductive biology of P. manillensis, we investigated floral traits, open fruit set, and flower visitors, and performed hand pollination and bagging experiments in five populations of Okinawa and Iriomote islands, Ryukyu Islands, Japan. The populations of P. manillensis were composed mainly of monoecious individuals (54%), followed by female (30%), male (14%), and hermaphroditic (2%) individuals at the time of flower collection. Of the collected flowers, 93% were functionally unisexual (male or female), whereas only 6.5% were perfect (hermaphroditic). However, some individuals changed sex mainly towards increasing femaleness during the flowering period. Moreover, 35% of the studied plants changed their sexual expression over the years. P. manillensis showed self-compatibility and no agamospermy. The fruit set under open pollination varied among populations and years (1.8–21.9%), but it was significantly higher than that of auto-selfing (0.68–1.56%). Wasps and flies were the main flower visitors and probably the main pollinators of the species. In conclusion, P. manillensis was revealed to be polygamous, involving monoecious, female, male, and hermaphroditic individuals. This is the first report of the polygamous breeding system not only in the genus Psychotria, but also in all heterostylous taxa.

Morphological and molecular phylogenetic analyses of Zepedanulus ishikawai (Arachnida: Opiliones: Laniatores: Epedanidae) in the southern part of the Ryukyu Archipelago

Harvestmen (Arachnida: Opiliones) are soil animals with extremely low dispersal abilities that experienced allopatric differentiation. To clarify the morphological and phylogenetic differentiation of the endemic harvestman Zepedanulus ishikawai (Suzuki, 1971) (Laniatores: Epedanidae) in the southern part of the Ryukyu Archipelago, we conducted molecular phylogenetic analyses and divergence time estimates based on CO1 and 16S rRNA sequences of mtDNA, the 28S rRNA sequence of nrDNA, and the external morphology. A phylogenetic tree based on mtDNA sequences indicated that individuals of Z. ishikawai were monophyletic and were divided into clade I and clade II. This was supported by the nrDNA phylogenetic tree. Although clades I and II were distributed sympatrically on all three islands examined (Ishigaki, Iriomote, and Yonaguni), heterogeneity could not be detected by polymerase chain reaction–restriction fragment length polymorphism of nrDNA, indicating that clades I and II do not have a history of hybridisation. Also, several morphological characters differed significantly between individuals of clade I and clade II. The longstanding isolation of the southern Ryukyus from the surrounding islands enabled estimation of the original morphological characters of both clades of Z. ishikawai.

The genus Rhyacophila Stephens (Trichoptera, Rhyacophilidae) in Yakushima Island, northern Ryukyu, southwestern Japan

This study revises the caddisfly genus Rhyacophila Stephens, Rhyacophilidae, for Yakushima Island within the northern Ryukyu Archipelago in southwestern Japan. Four new species are described based on adults: Rhyacophila yakushima sp. nov. of the R. anatina Species Group, R. arakawa sp. nov. of the R. lieftincki Species Group, R. miyanoura sp. nov. of the R. yosiiana Species Group, and R. nagata sp. nov. of the R. ulmeri Species Group. Additionally, two species are recorded for the island for the first time: R. brevicephala Iwata 1927, a Japanese species, and R. shikotsuensis Iwata 1927, an East Asian species.

First Record of the Soil-feeding Higher Termites (Isoptera: Termitidae) from Okinawa Island, the Central Ryukyus, Japan

Some of termites have been introduced outside their native ranges, and it has been suggested that both wood-eating and wood-nesting lifestyles are critical for the transportation of propagules. Here, we present the first record of the soil-feeding and soil-nesting termite Pericapritermes nitobei (Isoptera: Termitidae) in the Motobu Peninsula on the northern part of Okinawa Island in the Central Ryukyus. The fact that the previous extensive surveys of termites in the Ryukyu Archipelago did not detect P. nitobei in the Central Ryukyus, including the Motobu Peninsula, and its discontinuous distribution, indicate that P. nitobei has been recently introduced into the Motobu Peninsula of Okinawa Island from the Yaeyama Islands, similar to the fungus-growing and soil-nesting termite Odontotermes formosanus (Isoptera: Termitidae). Together with O. formosanus in the southern part of Okinawa Island, our findings in this study raise the possibility that non-wood-feeding and non-wood-nesting termites can be introduced and established outside their native ranges by human activities.

A new amphibious species of the genus Scolopendra Linnaeus, 1758 (Scolopendromorpha, Scolopendridae) from the Ryukyu Archipelago and Taiwan

In Japan and Taiwan, five valid species of the genus Scolopendra Linnaeus, 1758 have been described: S. morsitans Linnaeus, 1758, S. subspinipes Leach, 1816, S. mutilans Koch, 1878, S. japonica Koch, 1878, and S. multidens Newport, 1844. Recently, an undetermined species was found in the Ryukyu Archipelago and Taiwan. Using molecular phylogenetic analyses with mitochondrial COI and 16S rRNA and nuclear 28S rRNA and 18S rRNA genes as well as conventional morphological examination, we successfully discriminated this sixth species as an independent lineage from S. subspinipes, S. mutilans, and other named congeners from East and Southeast Asia. Therefore, the species was described as S. alcyona Tsukamoto & Shimano, sp. nov. Several situational evidences suggest that this species prefers streamside environments and exhibits amphibious behavior.