Cryptic hybridization between Common ( Apus apus) and Pallid ( A. pallidus) Swifts

• Published in: Ibis
• Main Authors: Cibois, Alice, Beaud, Michel, Foletti, Francesco, Gory, Gérard, Jacob, Gwenaël, Legrand, Nathalie, Lepori, Ludovic, Meier, Christoph, Rossi, Antoine, Wandeler, Peter, Thibault, Jean‐Claude
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2022
• Subjects: Apus apus
• Online Access: http://dx.doi.org/10.1111/ibi.13087; https://onlinelibrary.wiley.com/doi/pdf/10.1111/ibi.13087; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/ibi.13087

Artificial structures, and particularly in urban settings, attract species showing similar ecological niches and provide nest‐sites for cavity‐breeding species. It is, however, unknown whether this proximity creates opportunities for hybridization and gene flow across related species. We investigated whether two colonial species, the Common Swift Apus apus and the Pallid Swift Apus pallidus , are experiencing gene flow by genotyping individuals that breed in sympatry in the town of Bastia (Corsica, France). We compared them with individuals sampled in colonies where a single species is breeding, in the Mediterranean region and in Switzerland. Our results provided evidence of gene flow between the two species and showed that introgression was not limited to sympatric urban colonies. Gene flow was asymmetrical, with more Pallid Swifts than Common Swifts showing evidence of mixed ancestry. Several individuals were assessed as late‐generation hybrids, suggesting that introgression between the two species was associated with their range expansion since the Last Glacial Maximum. However, we also identified individuals that exhibit the characteristics of recent‐generation hybrids, particularly in Bastia. This result suggests that hybridization between the two species is an ongoing and underestimated phenomenon, with a single observation of a mixed pair in the literature, and may be favoured by close proximity in urban colonies.