Adaptive introgression between two Drosophila species enhances heat tolerance despite barriers to gene flow
4 affiliations
- 1Centre for Biological Diversity, University of St Andrews, St Andrews, United Kingdom
- 2Organismal and Evolutionary Biology Research Programme, University of Helsinki, Helsinki, Finland
- 3Zoology Institution, Stockholm University, Stockholm, Sweden
- 4Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands
Abstract
As global temperatures rise and heat waves become more frequent, populations must adapt rapidly to avoid local extinctions. Adaptive introgression allows species to quickly acquire adaptive genetic material from close relatives. However, certain genomic regions, containing barrier loci, may resist introgression. We experimentally tested whether strong heat stress selection can overcome such barriers and facilitate the transfer of adaptive alleles to improve heat tolerance. We also examined whether chromosomal inversions, which can tightly link adaptive and barrier loci through reduced recombination, promote or prevent introgression. We conducted a hybridize, evolve, and re-sequence experiment by crossing the heat-sensitive D. flavomontana with the more heat-tolerant D. montana, exposing heat-selection lines to transient heat for three generations while maintaining control lines. We also mapped long-term barriers to gene flow between natural populations using a demographically explicit genome scan. The heat-selection lines exhibited approximately twice the introgression and higher male fertility under heat stress compared to control lines and the heat-sensitive parental D. flavomontana. This introgression was primarily located in colinear autosomal regions and correlated with improved heat tolerance. Some introgression occurred also in inverted autosomal regions in the heat-selection lines but not in the control lines. The X chromosome, with three overlapping inversions, resisted introgression in both heat-selection and control lines, thereby maintaining a strong species barrier. Finally, genetic barriers in the control lines significantly overlapped with long-term barriers, but this overlap was less pronounced in the heat-selection lines. Our study demonstrates that strong selection can lead to adaptive introgression despite long-standing genetic barriers. These findings highlight that introgression can serve as a rapid source of adaptive genetic material under stressful thermal conditions, potentially mitigating climate-induced population extinctions.
As climate warming intensifies, it remains unclear whether adaptive introgression can overcome genomic barriers to spread beneficial alleles. This study shows that strong heat selection promotes introgression and heat tolerance despite long-standing barriers to gene flow.
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BibTeX
@article{poikela2026adaptive,
title = {{Adaptive introgression between two Drosophila species enhances heat tolerance despite barriers to gene flow}},
author = {Noora Poikela and Rhonda R. Snook and Jonna Kulmuni and Michael G. Ritchie},
journal = {PLOS Biology},
year = {2026},
month = sep,
doi = {10.1371/journal.pbio.3004028},
url = {https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3004028},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Adaptive introgression between two Drosophila species enhances heat tolerance despite barriers to gene flow
AU - Noora Poikela
AU - Rhonda R. Snook
AU - Jonna Kulmuni
AU - Michael G. Ritchie
PY - 2026
DA - 2026/09/30
JO - PLOS Biology
DO - 10.1371/journal.pbio.3004028
UR - https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3004028
AB - As global temperatures rise and heat waves become more frequent, populations must adapt rapidly to avoid local extinctions. Adaptive introgression allows species to quickly acquire adaptive genetic material from close relatives. However, certain genomic regions, containing barrier loci, may resist introgression. We experimentally tested whether strong heat stress selection can overcome such barriers and facilitate the transfer of adaptive alleles to improve heat tolerance. We also examined whether chromosomal inversions, which can tightly link adaptive and barrier loci through reduced recombination, promote or prevent introgression. We conducted a hybridize, evolve, and re-sequence experiment by crossing the heat-sensitive D. flavomontana with the more heat-tolerant D. montana, exposing heat-selection lines to transient heat for three generations while maintaining control lines. We also mapped long-term barriers to gene flow between natural populations using a demographically explicit genome scan. The heat-selection lines exhibited approximately twice the introgression and higher male fertility under heat stress compared to control lines and the heat-sensitive parental D. flavomontana. This introgression was primarily located in colinear autosomal regions and correlated with improved heat tolerance. Some introgression occurred also in inverted autosomal regions in the heat-selection lines but not in the control lines. The X chromosome, with three overlapping inversions, resisted introgression in both heat-selection and control lines, thereby maintaining a strong species barrier. Finally, genetic barriers in the control lines significantly overlapped with long-term barriers, but this overlap was less pronounced in the heat-selection lines. Our study demonstrates that strong selection can lead to adaptive introgression despite long-standing genetic barriers. These findings highlight that introgression can serve as a rapid source of adaptive genetic material under stressful thermal conditions, potentially mitigating climate-induced population extinctions. As climate warming intensifies, it remains unclear whether adaptive introgression can overcome genomic barriers to spread beneficial alleles. This study shows that strong heat selection promotes introgression and heat tolerance despite long-standing barriers to gene flow.
SN - 1545-7885
ER -