History of the terrestrial isopod genus Ligidium in Japan based on phylogeographic analysis.

BACKGROUND: Phylogeographical approaches explain the genetic diversity of local organisms in the context of their geological and geographic environments. Thus, genetic diversity can be a proxy for geological history. Here we propose a genus of woodland isopod, Ligidium, as a marker of geological history in relation to orogeny and the Quaternary glacial cycle. RESULTS: Mitochondrial analysis of 721 individuals from 97 sites across Japan revealed phylogenetic divergence between the northeastern and southwestern Japan arcs. It also showed repeated population expansions in northeastern Japan in response to Quaternary glacial and interglacial cycles. Genome-wide analysis of 83 selected individuals revealed multiple genetic nuclear clusters. The genomic groupings were consistent with the local geographic distribution, indicating that the Ligidium phylogeny reflects its regional history. CONCLUSION: Ligidium DNA sequence analysis can provide insight into the geological, geographical, and paleoenvironmental history of the studied region.

Sphaerillo boninensis Nunomura, 1990 (Crustacea, Isopoda, Oniscidea) is a junior synonym of a pantropical species, Venezillo parvus (Budde-Lund, 1885).

Re-examination of the holotype and paratype of Sphaerillo boninensis Nunomura, 1990 from Chichijima Island of the Ogasawara archipelago, which is registered as a UNESCO World Heritage Site, indicates that this species is a junior synonym of a pantropical species, Venezillo parvus (Budde-Lund, 1885).

Species compositions of terrestrial isopods in public parks of a commuter town in Japan.

The species compositions of terrestrial isopod assemblages in 150 public parks in a commuter town in Japan were investigated. Eleven species of terrestrial isopods were present, of which seven were considered native or oriental species, and four were exotic species originally distributed in the Mediterranean and European regions. An exotic species Armadillidiumvulgare Latreille, 1804 was found in all parks. Logistic model analysis indicated that the surrounding land use affected the distributions of three native species, Burmoniscuskathmandius (Schmalfuss, 1983), Ligidiumkoreanum Flasarova, 1972, and Mongoloniscuskoreanus Verhoeff, 1930, indicating that landscape properties are important factors that limit the distributions of terrestrial isopods. The present study also showed that the public parks surrounded by forests or semi-natural environments in a commuter town provide habitats for native terrestrial isopods.

Eleven nominal species of Burmoniscus are junior synonyms of B. kathmandius (Schmalfuss, 1983) (Crustacea, Isopoda, Oniscidea).

Holotypes, paratypes, and specimens newly collected from the type localities (i.e., topotypes) of Burmoniscus aokii (Nunomura, 1986), Burmoniscus boninensis (Nunomura, 1986), Burmoniscus daitoensis (Nunomura, 1986), Burmoniscus hachijoensis Nunomura, 2007, Burmoniscus japonicus (Nunomura, 1986), Burmoniscus kagoshimaensis Nunomura, 2003, Burmoniscus murotoensis (Nunomura, 1986), Burmoniscus okinawaensis (Nunomura, 1986), Burmoniscus shibatai (Nunomura, 1986), Burmoniscus tanabensis Nunomura, 2003, and Burmoniscus watanabei (Nunomura, 1986) were examined in order to clarify their taxonomic status. Observation of 13 morphological characters that were purposed to show species-level diagnostic variations in the original descriptions suggests that all eleven nominal species are identical, and molecular analysis based on three gene fragments supports this suggestion. Additionally, the morphology of the carpus of pereopod 1 and of the endo- and exopodites of pleopod 1 of these species are consistent with those of Burmoniscus kathmandius (Schmalfuss, 1983). The eleven above-mentioned species of Burmoniscus described from Japan are therefore relegated to junior synonyms of Burmoniscus kathmandius, originally reported from Nepal.

Phylogeographic Study of Whip Scorpions (Chelicerata: Arachnida: Thelyphonida) in Japan and Taiwan.

Whip scorpions (Thelyphonida), comprising an order in the class Arachnida, are distributed from tropical to temperate zones. Two species occur exclusively in Japan and Taiwan, but the border of their distributional ranges is ambiguous in the Central Ryukyus (Japan). We collected new specimens from the Central Ryukyus and revealed that the border of distribution of the two species lies between the Central and Southern Ryukyus, i.e., the Kerama Gap. Moreover, the estimated divergence time (15.8 Mya) of the two species, based on the mitochondrial COI gene, was older than the recently estimated time (1.55 Mya) of formation of the Kerama Gap. These results highlight the risks of a priori assumption solely on the basis of geological data for applying it as a calibration point to some terrestrial animals in this region. Typopeltis stimpsonii was genetically divided into four lineages, two of which turned out to be endemic to the Okinawa Islands. All specimens from the main island of Japan and Shikoku were in one lineage, which was also found in the Amami Islands and Hachijojima Island. This suggests that these specimens may have been dispersed by human activity. Typopeltis crucifer included five genetic lineages. Species collected from Ishigakijima and Iriomotejima Islands were genetically diversified not between the borders of these islands but within Ishigakijima Island. This study also suggests that phylogenetic diversity of the species in the Southern Ryukyus have increased through two times of invasions from Taiwan.

Burmoniscus kitadaitoensis Nunomura, 2009 (Crustacea, Isopoda, Oniscidea) from southern Japan, a junior synonym of B. meeusei (Holthuis, 1947).

Re-examination of the holotype of Burmoniscus kitadaitoensis Nunomura, 2009 from Kitadaitojima Island, southern Japan reveals that this species is a junior synonym of B. meeusei (Holthuis, 1947). Partial regions of mitochondrial COI, 12S and 16S rRNA genes, and nuclear 18S and 28S rRNA genes were detected for species identification in the future.

Taxonomic study of the Burmoniscus ocellatus complex (Crustacea, Isopoda, Oniscidea) in Japan shows genetic diversification in the southern Ryukyus, southwestern Japan.

To clarify the taxonomic status of the Burmoniscus ocellatus complex in Japan, we carried out morphological observations and phylogenetic analyses of specimens collected from Yonagunijima, Iriomotejima, Ishigakijima, and Miyakojima Islands of the southern Ryukyus and from Okinawajima Island of the central Ryukyus in southwestern Japan. Observations of the holotypes of Aphiloscia iriomotensis ( Nunomura, 1986 ), Ap. ishigakiensis ( Nunomura, 1986 ), and Ap. yonakuniensis ( Nunomura, 1986 ), in addition to the specimens newly collected from the five islands, indicated that these specimens belong to the genus Burmoniscus. Analyses of five morphological characters of 268 specimens collected from the five islands showed that the body size of Okinawajima specimens is distinctly smaller than those of the specimens from the southern Ryukyus. The ranges of the five morphological characters tended to overlap among the specimens from Yonagunijima, Iriomotejima, Ishigakijima and Miyakojima Islands; these morphological characters were congruent with those of 6. ocellatus (Verhoeff, 1928). The phylogenetic analyses were based on three regions of mitochondrial DNA-COI, 12S rRNA, and 16S rRNA-and indicated that the specimens collected from the southern Ryukyus constitute a monophyletic group, which is clearly distinct from the clade composed of the Okinawajima specimens. These results strongly suggest that Ap. iriomotensis, Ap. ishigakiensis, and Ap. yonakuniensis are synonymous with B. ocellatus, a species widely distributed in the southern Ryukyus. On the other hand, the species from Okinawajima Island in the central Ryukyus is considered to be an undescribed Burmoniscus species, which is closely related to but clearly distinct from S. ocellatus.

Description of a sexually dimorphic oribatid mite (Arachnida: Acari: Oribatida) from canopy habitats of the Ryukyu Archipelago, southwestern Japan.

A new species in the monotypic genus Symbioribates, S. aokii sp. nov., is described on the basis of adult material collected from canopy habitats and wind traps in the Ryukyu Archipelago, southwestern Japan. Symbioribates aokii sp. nov. expresses different dimorphism in the octotaxic system from that of the type species, S. papuensis Aoki, 1966. The characteristics of this genus and its relationships to others of the superfamily Oripodoidea are discussed and a revised diagnosis of the family is given.