25Proc. Arthropod. Embryol. Soc. Jpn. 49, 25 (2016)Ⓒ 2016 Arthropodan Embryological Society of Japan
ISSN 1341–1527

Molecular Phylogeny of Three Soil-dwelling Species of the Genus
Mundochthonius in Japan (Pseudoscorpiones: Chthoniidae)*Hajime OHIRA1), Shingo KANEKO2) and Tadaaki TSUTSUMI2)
Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima, Fukushima
960–1296, Japan.
2)
Department of Environmental System Management, Faculty of Symbiotic Systems Science, Cluster of Science and Technology,Fukushima University, 1 Kanayagawa, Fukushima, Fukushima 960–1296, Japan.
E-mail: ohira.hajime@gmail.com (HO)1)

The genus Mundochthonius is a group of pseudoscorpionsof small body size (less than ca. 1 mm in body length). They
are usually found in forest soil (litter) and occasionally incaves. Twenty-four species have been described from Asia,
North America, and Europe. Three species and threesubspecies endemic to Japan have been recorded: M.
japonicus japonicus Chamberlin, 1929 (soil-dwelling), M.
japonicus scolytidis Morikawa, 1954 (soil-dwelling), M.
japonicus imadatei Morikawa, 1956 (cavernicolous), M.
japonicus tripartitus, 1956 (cavernicolous), M. kiyoshii
Sakayori, 2002 (soil-dwelling), and M. itohi Sakayori, 2009
(soil-dwelling). The soil-dwelling Japanese species have beenclassified on the basis of the following morphologicalcharacters: body length, carapacal chaetotaxy, abdominal
tergal chaetotaxy, and proportions of the pedipalpal femur.
These characters are, however, highly variable, and theirvariations overlap among species. Conversely, the threesubspecies of M. japonicus exhibit morphological differences
equivalent to those found at the species level. In the present
study, we conducted a molecular phylogenetic analysis ofJapanese Mundochthonius species and subspecies using
mitochondrial cytochrome c oxidase subunit I (COI) andnuclear 18S rRNA genes as genetic markers and performed aprincipal component analysis (PCA) for 19 morphologicalcharacters to clarify the phylogeny of these species andreevaluate their taxonomy.
For use in the phylogenetic analysis and PCA, we
sampled 57 specimens of soil-dwelling Mundochthonius
species. The samples were collected from 20 localities in thedistribution range of the genus in Japan [from Hokkaido toYakushima (Kagoshima Prefecture)].
In molecular phylogenetic trees based on COI and 18SrRNA genes, five major clades (clades 1–5) were recognizedusing either locus. Although the OTUs included within eachclade were identical in both trees, the relationships of themajor clades differed. The five clades were divided into threegroups based on body size: clade 1, clades 2+5 and clades
3+4. Individuals morphologically identifiable as the threesoil-dwelling species M. japonicus scolytidis, M. kiyoshii andM. itohi were included in each group, but the PCA did notclassify these three groups as separate species. We thenlooked for morphological differences among the samples
included in each clade. In clades 2 and 3, we foundmorphological characteristics qualitatively different from thesamples included in clades 1, 4 and 5. The five clades can beclassified into the following taxonomic groups: clade 1, M.
itohi; clade 2, M. sp. MA (similar to M. kiyoshii, but
distinguishable from M. kiyoshii by the number of anterior
setae on the external genital pouch); clade 3, M. sp. MB(similar to M. japonicus scolytidis, but distinguishable by theshape of the knob-like protuberance on top of the cheliceralmovable finger); clade 4, M. japonicus scolytidis; and clade 5,M. kiyoshii.
Wider geographical sampling of Mundochthonius
species, as well as molecular phylogenetic analyses using
additional loci and phylogenetic tree reconstruction methods,
will improve our future studies and verify the phylogenetic
relationships of soil-dwelling species of Japanese
Mundochthonius.

* Abstract of paper read at the 50th Annual Meeting of the Arthropodan Embryological Society of Japan, July 3–4, 2014 (Fuchu, Tokyo).