When Hybrids Take an Intermediate Route: Genetic Ancestry Shapes Migration Across a Seabird Contact Zone.
8 affiliations
- 1Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Facultat de Biologia, Universitat de Barcelona (UB), Barcelona, Spain.
- 2Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona (UB), Barcelona, Spain.
- 3Dipartimento di Scienze e Politiche Ambientali, Università Degli Studi di Milano, Milano, Italy.
- 4Department of Biology, Colorado State University, Fort Collins, Colorado, USA.
- 5Dipartimento di Scienze Della Vita e Dell'ambiente, Università Politecnica Delle Marche, Ancona, Italy.
- 6Asociación de Naturalistas del Sureste (ANSE), Murcia, Spain.
- 7CSIC, Institut de Ciències del Mar (ICM), Barcelona, Spain.
- 8Department of Conservation Biology, Estación Biológica de Doñana (CSIC), Sevilla, Spain.
Abstract
Contact zones, where related taxa breed sympatrically, provide natural laboratories for studying phylogeography and speciation. In migratory species, these systems offer unique opportunities to disentangle the relative roles of genetic and social factors in migratory behaviour. Cory's (Calonectris borealis) and Scopoli's shearwaters (C. diomedea) are closely related long-distance migrants that breed allopatrically across most of their ranges but occur sympatrically in the Alboran Sea. Here, we tested whether the migratory strategies of these shearwaters are determined primarily by their genetic ancestry or by the social environment of their breeding colony. We used light-level geolocators to track the annual migration of 50 individuals (127 tracks) from six breeding colonies: four sympatric colonies within the Alboran contact zone and one allopatric colony of each species. We also generated whole-genome sequencing data for 58 individuals (including all 50 tracked birds) to infer species ancestry and identify hybrids. Most Cory's shearwaters wintered in subtropical Atlantic upwelling systems along the African and South American coasts, whereas most Scopoli's shearwaters wintered in tropical waters off West Africa. The two taxa partially overlapped in the Sahelian upwelling and Angolan waters. Individuals breeding in the contact zone exhibited migration strategies that matched their genomic ancestry rather than the colony's predominant pattern. Most importantly, we identified seven recent hybrids between the two taxa, representing 17.5% of the sampled individuals in the contact zone. These hybrids exhibited intermediate migratory strategies, indicating a strong genetic determination of migratory behaviour. The overlap in wintering areas may increase opportunities for interspecific interactions before arrival at the breeding colonies, potentially promoting hybridisation. Our study demonstrates that migratory strategies are strongly influenced by genetic background in long-distance migratory seabirds and suggests that weak migratory connectivity among populations facilitates hybridisation in contact zones.
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BibTeX
@article{garciaurdangarin2026when,
title = {{When Hybrids Take an Intermediate Route: Genetic Ancestry Shapes Migration Across a Seabird Contact Zone.}},
author = {Beñat Garcia-Urdangarin and Joan Ferrer Obiol and Josephine R Paris and Ángel Sallent and Guillem Izquierdo-Arànega and Marc Ragonnet and Isabel Afán and Manuela G Forero and Joan Navarro and Pedro García and Jacob González-Solís and Raül Ramos},
journal = {Molecular ecology},
year = {2026},
month = oct,
doi = {10.1111/mec.70598},
url = {https://europepmc.org/article/MED/42902923},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - When Hybrids Take an Intermediate Route: Genetic Ancestry Shapes Migration Across a Seabird Contact Zone.
AU - Beñat Garcia-Urdangarin
AU - Joan Ferrer Obiol
AU - Josephine R Paris
AU - Ángel Sallent
AU - Guillem Izquierdo-Arànega
AU - Marc Ragonnet
AU - Isabel Afán
AU - Manuela G Forero
AU - Joan Navarro
AU - Pedro García
AU - Jacob González-Solís
AU - Raül Ramos
PY - 2026
DA - 2026/10/01
JO - Molecular ecology
DO - 10.1111/mec.70598
UR - https://europepmc.org/article/MED/42902923
AB - Contact zones, where related taxa breed sympatrically, provide natural laboratories for studying phylogeography and speciation. In migratory species, these systems offer unique opportunities to disentangle the relative roles of genetic and social factors in migratory behaviour. Cory's (Calonectris borealis) and Scopoli's shearwaters (C. diomedea) are closely related long-distance migrants that breed allopatrically across most of their ranges but occur sympatrically in the Alboran Sea. Here, we tested whether the migratory strategies of these shearwaters are determined primarily by their genetic ancestry or by the social environment of their breeding colony. We used light-level geolocators to track the annual migration of 50 individuals (127 tracks) from six breeding colonies: four sympatric colonies within the Alboran contact zone and one allopatric colony of each species. We also generated whole-genome sequencing data for 58 individuals (including all 50 tracked birds) to infer species ancestry and identify hybrids. Most Cory's shearwaters wintered in subtropical Atlantic upwelling systems along the African and South American coasts, whereas most Scopoli's shearwaters wintered in tropical waters off West Africa. The two taxa partially overlapped in the Sahelian upwelling and Angolan waters. Individuals breeding in the contact zone exhibited migration strategies that matched their genomic ancestry rather than the colony's predominant pattern. Most importantly, we identified seven recent hybrids between the two taxa, representing 17.5% of the sampled individuals in the contact zone. These hybrids exhibited intermediate migratory strategies, indicating a strong genetic determination of migratory behaviour. The overlap in wintering areas may increase opportunities for interspecific interactions before arrival at the breeding colonies, potentially promoting hybridisation. Our study demonstrates that migratory strategies are strongly influenced by genetic background in long-distance migratory seabirds and suggests that weak migratory connectivity among populations facilitates hybridisation in contact zones.
SN - 0962-1083
SN - 1365-294X
ER -