Climate change is driving drastic environmental shifts and accelerating global biodiversity loss. Hybrid introgression has recently been recognized as an important mechanism facilitating rapid adaptation to historic climate change. However, empirical evidence remains lacking as to whether introgression can enhance future climate resilience, particularly for narrow-ranged species inhabiting mountainous regions that serve as biodiversity hotspots.

To address this gap in knowledge, a research team led by QU Yanhua from the Institute of Zoology, Chinese Academy of Sciences focused on three closely related birds of the Sino-Himalayan mountains — Alcippe hueti, A. davidi, and A. fratercula. By integrating population and ecological genomic approaches, they found that interspecific introgression can reduce climate change vulnerability in montane birds. This study was published in Nature Climate Change (https://www.nature.com/articles/s41558-025-02485-w).

The results showed that the three species began to diverge around 220,000 years ago, and continuous gene flow among parapatric species started approximately 47,000 years ago. Using machine learning methods, the researchers precisely identified introgressed genomic segments and their directions. A. davidi and A. hueti have more introgressed segments due to higher gene flow levels.

During the divergence, the three species gradually occupied distinct climatic niches: the eastern A. davidi favors warm and humid environments, the western A. fratercula adapts to cooler and drier conditions, and the central A. hueti occupies an intermediate niche. In the future, all three species are projected to face severe climatic challenges, potentially losing 44–69% of their suitable habitats.

Furthermore, the team found that about 28.5% of climate-adaptive loci were located within introgressed genomic regions (i.e., introgressed climate-associated SNPs), and show strong signals of natural selection. Hybrid individuals exhibited higher nucleotide diversity at these loci and required fewer genetic changes to cope with future climatic shifts, reflecting lower climate vulnerability. Population genetic simulations also supported these findings: under a continuous gene flow model, species fitness could recover after approximately 25 generations under future climate scenarios, whereas fitness recovery was extremely limited under a non-gene-flow model.

This study demonstrates that hybrid introgression is a crucial evolutionary mechanism enhancing species’ capacity to adapt to climate change, and highlight the importance of preserving migration corridors and contact zones, which are vital for facilitating interspecific genetic material exchange and restoring population fitness.

Interspecific introgression mitigates the climate change risk (image by QU’ Lab)