From Continental Relicts to Island Neoendemics: Ancient Persistence and Multi‐Stage Diversification of Scutigeromorph Centipedes in the Japanese Archipelago
Bin Ye, Shun Ito, Takahiro Hirano, Daishi Yamazaki, Isao Sano, Osamu Kagawa, Komei Endo, Xia Wan, Satoshi ChibaABSTRACT
Aim
To test the hypothesis that the Japanese Archipelago has acted as a biogeographic ‘museum’ preserving ancient continental lineages, using scutigeromorph centipedes as a model and to reconstruct the region's multi‐stage biogeographic history by distinguishing between paleoendemic relicts and neoendemic radiations.
Location
Continental East Asia (focusing on China) and the Japanese Archipelago (including mainland and isolated islands).
Methods
We generated a comprehensive multi‐locus molecular dataset from extensive sampling across the region. We reconstructed a time‐calibrated phylogeny using Bayesian methods with fossil‐calibrated node dating to estimate divergence times. Phylogeographic structure, demographic history and lineage diversification patterns were analysed to infer biogeographic processes.
Results
The phylogeny confirmed the monophyly of the genera Thereuopoda and Thereuonema and revealed a deep, consistent phylogeographic break within two widespread species. This break separates a continental lineage (including populations from the continental East Asian and the Japanese isolated islands) from an endemic clade on the Japanese mainland. Divergence time estimates for these primary splits (~100–98 Ma) substantially predate the Miocene formation of the Japanese Archipelago (~25–15 Ma), supporting its role as a biogeographic ‘museum’ for ancient continental lineages. Notably, biogeographic model selection strongly supported a scenario of dispersal from the Japanese isolated islands to the Japanese mainland within the archipelago. Demographic expansions correlate with periods of geological stabilisation. Analyses further uncovered pronounced genetic structure indicative of unrecognised diversity.
Main Conclusion
Our findings provide strong support for the ‘museum’ hypothesis, demonstrating that the Japanese Archipelago harbours ancient continental lineages preserved via vicariance and long‐term refugial persistence (paleoendemism). This ancient fauna was subsequently supplemented by in situ diversification following isolation, generating neoendemic clades. The study reveals a complex, multi‐stage assembly history for the region's biota, challenging purely dispersal‐driven narratives and highlighting the critical role of ancient vicariance and landmass permanence in shaping East Asian biodiversity.