| 要旨トップ | 目次 | | 日本生態学会第73回全国大会 (2026年3月、京都) 講演要旨 ESJ73 Abstract

一般講演（ポスター発表） P2-052 （Poster presentation）

#### 琉球列島における表層性トビムシの一種 Tomocerus cf. ocreatus の種分化【E】
Species differentiation of Tomocerus cf. ocreatus, a surface-dwelling collembolan, along the Ryukyu Archipelago【E】

高江洌鈴奈（横浜国立大学, 沖縄国際大学）, 富盛一（沖縄国際大学）, 新垣征士（沖縄国際大学）, 金城幸宏（沖縄国際大学, 沖縄科技大）, 中森泰三（横浜国立大学）, *齋藤星耕（沖縄国際大学）
Reina TAKAESU（Yokohama National Univ, Okinawa Intl Univ）, Kazu TOMIMORI（Okinawa Intl Univ）, Seiji ARAKAKI（Okinawa Intl Univ）, Yukihiro KINJO（Okinawa Intl Univ, Okinawa Inst of Sci and Tech）, Taizo NAKAMORI（Yokohama National Univ）, *Seikoh SAITOH（Okinawa Intl Univ）

Collembola are minute, wingless hexapods that inhabit soil and surface litter environments. Owing to their limited dispersal capacity, populations on oceanic islands are likely to experience geographic isolation, promoting genetic structuring and potentially lineage divergence. We investigated patterns of genetic differentiation and phylogenetic relationships in the surface-dwelling species Tomocerus cf. ocreatus across the Ryukyu Archipelago of southwestern Japan.
To assess population structure, we analyzed six mitochondrial and nuclear loci from specimens collected on multiple islands spanning approximately 800 km, from Yonaguni Island to Amami-Oshima. Phylogenetic reconstruction showed that the Ryukyu populations form a well-supported monophyletic lineage that is sister to a mainland Chinese clade comprising T. qinae and T. pseudocreatus. Levels of sequence divergence among islands suggest that the Ryukyu populations may represent two or three independently evolving lineages. Furthermore, genetic distances at individual loci were positively correlated with geographic separation among sampling sites.
Complete mitochondrial genomes were additionally obtained from two populations on Okinawa Island, sampled from its northern and southern regions. Each mitogenome comprised the typical 37 genes (13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes). Comparative analyses revealed mean sequence identities of 92.5% in protein-coding regions, 96.0% in rRNA genes, and 98.0% in tRNA genes, indicating substantial intraspecific divergence even within a single island. This high level of mitochondrial variability suggests that the cytochrome c oxidase subunit I (COI) gene, widely used for DNA barcoding in animals, may have limited resolution for delimiting conspecific populations in this taxon.
By the time of presentation, additional sequence data from a more northern island (Yakushima) will be incorporated to further evaluate latitudinal patterns of diversification. Overall, our results demonstrate pronounced genetic structuring both within and among islands in the Ryukyu Archipelago, consistent with ongoing or historical processes of species differentiation in this surface-dwelling collembolan.

日本生態学会