Additive Traits Lead to Feeding Advantage and Reproductive Isolation, Promoting Homoploid Hybrid Speciation

• Published in: Molecular Biology and Evolution
• Main Authors: Masello, Juan F, Quillfeldt, Petra, Sandoval-Castellanos, Edson, Alderman, Rachael, Calderón, Luciano, Cherel, Yves, Cole, Theresa L, Cuthbert, Richard J, Marin, Manuel, Massaro, Melanie, Navarro, Joan, Phillips, Richard A, Ryan, Peter G, Shepherd, Lara D, Suazo, Cristián G, Weimerskirch, Henri, Moodley, Yoshan
• Other Authors: Russo, Claudia, Deutsche Forschungsgemeinschaft, Heisenberg program, Natural Environment Research Council, Institut Polaire Français Paul Emile Victor, Terres Australes et Antarctiques Françaises, Mohamed bin Zayed Species Conservation Fund and the Brian Mason Scientific and Technical Trust, Chatham Islands, Falkland Islands Government, Government of South Georgia and the South Sandwich Islands, Animal Ethic Committee of the Institut Polaire Français Paul Emile Victor, Préfet des Terres Australes et Antarctiques Françaises, Animal Ethics Committee of Charles Sturt University, New Zealand Department of Conservation, New Island Conservation Trust, Antarctic Research Trust
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2019
• Subjects: Genetics; Molecular Biology; Ecology, Evolution, Behavior and Systematics; Antarc*; Antarctic; Antarctic prion; Pachyptila desolata
• Online Access: http://dx.doi.org/10.1093/molbev/msz090; http://academic.oup.com/mbe/advance-article-pdf/doi/10.1093/molbev/msz090/28790181/msz090.pdf; http://academic.oup.com/mbe/article-pdf/36/8/1671/29001242/msz090.pdf

Abstract Speciation through homoploid hybridization (HHS) is considered extremely rare in animals. This is mainly because the establishment of reproductive isolation as a product of hybridization is uncommon. Additionally, many traits are underpinned by polygeny and/or incomplete dominance, where the hybrid phenotype is an additive blend of parental characteristics. Phenotypically intermediate hybrids are usually at a fitness disadvantage compared with parental species and tend to vanish through backcrossing with parental population(s). It is therefore unknown whether the additive nature of hybrid traits in itself could lead successfully to HHS. Using a multi-marker genetic data set and a meta-analysis of diet and morphology, we investigated a potential case of HHS in the prions (Pachyptila spp.), seabirds distinguished by their bills, prey choice, and timing of breeding. Using approximate Bayesian computation, we show that the medium-billed Salvin’s prion (Pachyptila salvini) could be a hybrid between the narrow-billed Antarctic prion (Pachyptila desolata) and broad-billed prion (Pachyptila vittata). Remarkably, P. salvini’s intermediate bill width has given it a feeding advantage with respect to the other Pachyptila species, allowing it to consume a broader range of prey, potentially increasing its fitness. Available metadata showed that P. salvini is also intermediate in breeding phenology and, with no overlap in breeding times, it is effectively reproductively isolated from either parental species through allochrony. These results provide evidence for a case of HHS in nature, and show for the first time that additivity of divergent parental traits alone can lead directly to increased hybrid fitness and reproductive isolation.