The genetics of extrinsic postzygotic selection in a migratory divide between subspecies of the Swainson’s thrush
Abstract Extrinsic postzygotic isolation, where hybrids experience reductions in fitness due to a mismatch with their environment, is central to speciation. Knowledge of genetic variants that underlie extrinsic isolation is crucial for understanding the early stages of speciation. Differences in sea...
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Nature Portfolio
2025-08-01
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| Series: | Nature Communications |
| Online Access: | https://doi.org/10.1038/s41467-025-63188-6 |
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| author | Hannah C. Justen Stephanie A. Blain Kira E. Delmore |
| author_facet | Hannah C. Justen Stephanie A. Blain Kira E. Delmore |
| author_sort | Hannah C. Justen |
| collection | DOAJ |
| description | Abstract Extrinsic postzygotic isolation, where hybrids experience reductions in fitness due to a mismatch with their environment, is central to speciation. Knowledge of genetic variants that underlie extrinsic isolation is crucial for understanding the early stages of speciation. Differences in seasonal migration are strong candidates for extrinsic isolation (e.g., if hybrids take intermediate and inferior routes compared to pure forms). Here, we used a hybrid zone between two subspecies of the songbird Swainson’s thrush (Catharus ustulatus) with different migratory routes and tests for viability selection (locus-specific changes in interspecific heterozygosity and ancestry mismatch across age classes) to gain insight into the genetic basis of extrinsic isolation. Using data from over 900 individuals we find strong evidence for viability selection on both interspecific heterozygosity and ancestry mismatch at loci linked to migration. Much of this selection was dependent on genome-wide ancestry; as expected, a subset of hybrids exhibited reduced viability, but remarkably, another subset appears to fill an unoccupied fitness peak within the species, exhibiting higher viability than even parental forms. Many of the variants that influence hybrid viability appear to occur in structural variants, including a putative pericentric inversion. Our study emphasizes the importance of epistatic interactions and structural variants in speciation. |
| format | Article |
| id | doaj-art-e44a7f444c014f8d96496e1af7ed7c63 |
| institution | Kabale University |
| issn | 2041-1723 |
| language | English |
| publishDate | 2025-08-01 |
| publisher | Nature Portfolio |
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| series | Nature Communications |
| spelling | doaj-art-e44a7f444c014f8d96496e1af7ed7c632025-08-24T11:38:08ZengNature PortfolioNature Communications2041-17232025-08-0116111110.1038/s41467-025-63188-6The genetics of extrinsic postzygotic selection in a migratory divide between subspecies of the Swainson’s thrushHannah C. Justen0Stephanie A. Blain1Kira E. Delmore2Neurobiology, Physiology and Behavior Department, University of CaliforniaEcology and Evolutionary Biology Department, Columbia UniversityEcology and Evolutionary Biology Department, Columbia UniversityAbstract Extrinsic postzygotic isolation, where hybrids experience reductions in fitness due to a mismatch with their environment, is central to speciation. Knowledge of genetic variants that underlie extrinsic isolation is crucial for understanding the early stages of speciation. Differences in seasonal migration are strong candidates for extrinsic isolation (e.g., if hybrids take intermediate and inferior routes compared to pure forms). Here, we used a hybrid zone between two subspecies of the songbird Swainson’s thrush (Catharus ustulatus) with different migratory routes and tests for viability selection (locus-specific changes in interspecific heterozygosity and ancestry mismatch across age classes) to gain insight into the genetic basis of extrinsic isolation. Using data from over 900 individuals we find strong evidence for viability selection on both interspecific heterozygosity and ancestry mismatch at loci linked to migration. Much of this selection was dependent on genome-wide ancestry; as expected, a subset of hybrids exhibited reduced viability, but remarkably, another subset appears to fill an unoccupied fitness peak within the species, exhibiting higher viability than even parental forms. Many of the variants that influence hybrid viability appear to occur in structural variants, including a putative pericentric inversion. Our study emphasizes the importance of epistatic interactions and structural variants in speciation.https://doi.org/10.1038/s41467-025-63188-6 |
| spellingShingle | Hannah C. Justen Stephanie A. Blain Kira E. Delmore The genetics of extrinsic postzygotic selection in a migratory divide between subspecies of the Swainson’s thrush Nature Communications |
| title | The genetics of extrinsic postzygotic selection in a migratory divide between subspecies of the Swainson’s thrush |
| title_full | The genetics of extrinsic postzygotic selection in a migratory divide between subspecies of the Swainson’s thrush |
| title_fullStr | The genetics of extrinsic postzygotic selection in a migratory divide between subspecies of the Swainson’s thrush |
| title_full_unstemmed | The genetics of extrinsic postzygotic selection in a migratory divide between subspecies of the Swainson’s thrush |
| title_short | The genetics of extrinsic postzygotic selection in a migratory divide between subspecies of the Swainson’s thrush |
| title_sort | genetics of extrinsic postzygotic selection in a migratory divide between subspecies of the swainson s thrush |
| url | https://doi.org/10.1038/s41467-025-63188-6 |
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