Male-Biased Dispersal Leads to Expansion After Decline: The Hokkaido Brown Bear (Ursus arctos) Population Rebounds Post-Last Glacial Period.

Authors

Yu Endo, Naoki Osada, Tsutomu Mano, Atsushi J Nagano, Ryuichi Masuda

Published in

Ecology and evolution. Volume 16. Issue 9. Pages e74312. Epub Sep 20, 2026.

Abstract

Sex-biased dispersal potentially underpins the genetic structural mismatch in genetic structure between differently inherited genetic loci, but accurately evaluating the effect of sex-biased dispersal is challenging due to other sex-biased traits and limitations in usable data. Brown bears exhibit extreme male-biased dispersal, with significant genetic differences between maternally and paternally inherited loci. This study aims to investigate how the characteristic genetic structure in Hokkaido, Japan has been shaped and to evaluate the influence of male-biased dispersal and environmental barriers on this process. We conducted a reduced-representation genome sequencing, ddRAD-seq, and combined it with mitochondrial DNA and Y chromosomal haplotype data. Genetic differences between the southern subpopulations and the other subpopulations were observed, which may reflect restricted gene flow, particularly among female bears, as a consequence of lowland barriers. The ratio of genetic differentiation between the X-chromosome and autosomes suggests a significant effect of male-biased dispersal within the Hokkaido population, with slight variation in this effect among subpopulations. Species distribution modeling estimated that suitable habitat decreased during the Last Glacial Period, and demographic simulation inferred a historical population decline during this period, followed by population expansion. These results suggest that the Hokkaido population had contracted and isolated in spite of the appearance of the land bridge and has expanded after that while being limited by the lowlands. Male-biased dispersal likely contributed to population recolonization after significant population decline and habitat reduction due to climate changes.

PMID:
42769017
Bibliographic data and abstract were imported from PubMed on 22 Sep 2026.

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