Tracing the origin and persistence of introgressive hybrids of two salmonid species, Salvelinus curilus and S. leucomaenis, in allopatric habitats

Authors

• Shoichiro Yamamoto, Japan Fisheries Research and Education Agency
• Shujuan Xia, University of Tokyo, Japan
• Kousei Fukuzawa, University of Tokyo, Japan
• Kentaro Morita, University of Tokyo, Japan
• Satoshi Kitano, Nagano Prefecture Lake Suwa Environmental Research Center, Japan
• Masashi Sekino, Japan Fisheries Research and Education Agency
• Yoshiyuki Umatani, Hokkaido Univerity, Japan
• Uli Reinhardt, Eastern Michigan University
• Koji Maekawa, Hokkaido Univerity, Japan

Document Type

Article

Publication Date

2026

Department/School

Biology

Publication Title

Biological Journal of the Linnean Society

Abstract

Unravelling the origin and mechanisms of interspecific hybridization and clarifying its evolutionary and ecological consequences constitutes a central theme in evolutionary biology. This study elucidates the origin and mechanisms underlying the persistence of individuals carrying intro- gressed alleles resulting from historical hybridization between two closely related salmonid species, Salvelinus curilus and S. leucomaenis, in a region where the donor species is now absent. We employed two complementary approaches. First, we conducted a comprehensive comparative phylo- geographical analysis across the full geographical ranges of both species to characterize spatial patterns of historical hybridization and infer the origin of introgressed individuals. Second, we developed and applied evolutionary models based on the Wright–Fisher model to evaluate whether the persistence of these individuals is explained by the combined effects of genetic drift and natural selection. Introgressed individuals carried a single mitochondrial DNA haplotype substantially divergent from the recipient species (S. curilus) and matching a haplotype of the donor species (S. leucomaenis) that occurs in areas geographically distant from the current distribution of introgressed individuals. Simulation-based analyses indicated that the observed frequencies of introgressed individuals can be explained largely by genetic drift. Although a model incorporating both genetic drift and selection provided a modestly better fit to the data, support for selection was suggestive rather than conclusive. Even under a weak selective disadvantage, the stochastic effects of genetic drift may allow these individuals to persist over multiple generations, particularly in small populations.

Comments

U. Reinhardt is a faculty member in EMU's Department of Biology.

Link to Published Version

DOI: 10.1093/biolinnean/blag026

Recommended Citation

Yamamoto, S., Xia, S., Fukuzawa, K., Morita, K., Kitano, S., Sekino, M., Umatani, Y., Reinhardt, U., & Maekawa, K. (2026). Tracing the origin and persistence of introgressive hybrids of two salmonid species, Salvelinus curilus and S. leucomaenis, in allopatric habitats. Biological Journal of the Linnean Society, 148(1), blag026. https://doi.org/10.1093/biolinnean/blag026