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Two Polish European Roe Deer Haplotypes Fell Within Siberian Roe Deer Maternal Lineages

Male European roe deer in woodland in Łódź, Poland
Research · Genetics & genomics

Complete mitochondrial genomes revealed maternal-line evidence of genetic exchange between European roe deer (Capreolus capreolus) and Siberian roe deer (Capreolus pygargus). Mitochondrial DNA is inherited through the maternal line in these mammals, so a mitogenome traces the ancestry of the mother’s mitochondrial lineage rather than the animal’s whole nuclear genome. A study published on 17 June 2026 found two Polish European roe deer haplotypes nested within Siberian roe deer mitochondrial lineages.

The researchers sequenced 52 complete European roe deer mitogenomes from Slovenia, Poland and France and combined them with 24 previously available genomes from European and Siberian roe deer. The final dataset contained 76 genomes representing 59 mitochondrial haplotypes. A haplotype is a distinct mitochondrial sequence variant that represents one maternal genetic lineage. European roe deer showed high haplotype diversity but low nucleotide diversity: many different maternal variants were present, yet the average sequence differences among them were relatively small. Although that pattern can be consistent with demographic expansion, the study’s formal demographic tests did not provide clear statistical support for a recent expansion.

Two Polish haplotypes carried Siberian-lineage mitochondria

The analysis recovered the three major mitochondrial clades already recognised in European roe deer: Eastern, Central and Western. It also found Central-clade haplotypes in France. Most strikingly, two Polish European roe deer haplotypes, Cp9 and Cp10, clustered within an established Siberian roe deer mitochondrial clade together with previously reported Russian and Polish haplotypes. This pattern supports mitochondrial introgression — movement of mitochondrial DNA from one species into another through hybridisation followed by backcrossing.

The time-calibrated phylogeny is consistent with these introgressed haplotypes belonging to an established Siberian maternal lineage rather than simply arising from a recent mutation within European roe deer. The authors argue that older natural hybridisation during glacial-range shifts is a plausible source, although historical human-mediated translocations may also have contributed to introgression elsewhere. Crucially, mitochondrial dating estimates when lineages shared ancestors, not the date of the hybridisation event itself, so whole-genome demographic analyses would be needed to distinguish ancient from recent introgression more directly.

Little evidence that the introgressed mitochondria were strongly adaptive

The authors conclude that whole mitogenomes sharpen the phylogeographic picture of European roe deer by revealing maternal lineages that shorter mitochondrial markers may not resolve as clearly. Tests of mitochondrial protein-coding genes found only limited evidence of episodic positive selection at a small number of codons and little evidence for widespread adaptive change. The broader pattern is therefore compatible with much of the mitochondrial exchange being evolutionarily neutral rather than the Siberian-lineage mitochondria necessarily spreading because they provided a strong fitness advantage.

Sources and image credit

  1. Buzan, E., Cidilko, S., Duniš, L., Komel, T., Pokorny, B., Hewison, A. J. M., & Korzekwa, A. (2026). Introgression among maternal lineages inferred from complete mitogenomes and molecular dating helps resolve phylogeography of European roe deer. BMC Ecology and Evolution. https://doi.org/10.1186/s12862-026-02540-wPrimary peer-reviewed open-access study published 17 June 2026 under CC BY 4.0. The authors analysed 52 newly sequenced European roe deer mitogenomes from Slovenia, Poland and France together with 24 public European and Siberian roe deer genomes.

Image: Jerzy Strzelecki / Wikimedia Commons — male European roe deer (Capreolus capreolus) photographed in Łódź, Poland, 6 May 2020. Representative image for this story; not presented as an animal or scene from the reported study or event. · CC BY-SA 3.0 · Source

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