Nwankwo, Emmanuel C.Mortega, Kim G.Karageorgos, AthanasiosOgolowa, Bridget O.Papagregoriou, GregoryGrether, Gregory F.Monadjem, AraKirschel, Alexander N.G.2019-10-092019-04Nwankwo, E.C., Mortega, K.G., Karageorgos, A. et al. 2019, 'Rampant introgressive hybridization in Pogoniulus tinkerbirds (Piciformes: Lybiidae) despite millions of years of divergence', Biological Journal of the Linnean Society, vol. 127, no. 1, pp. 125-142.0024-4066 (print)1095-8312 (online)10.1093/biolinnean/blz018http://hdl.handle.net/2263/71647Incomplete reproductive isolation between related species of birds at contact zones is increasingly being documented. Such hybridization typically occurs between sister taxa that diverged in relatively recent times, and hybrids are most often identified based on their intermediate phenotypic characteristics and, increasingly, through genetic admixture analysis. When species have been diverging over relatively longer time scales, prezygotic isolation barriers are expected to evolve, precluding maladaptive interbreeding. Here, we examine the extent of introgressive hybridization in a pair of African barbets, the yellow-fronted tinkerbird (Pogoniulus chrysoconus extoni) and the red-fronted tinkerbird (Pogoniulus pusillus pusillus), which were not previously known to interbreed, across a contact zone in Southern Africa. Although there were significant differences in the coloration of plumage between the species, we found a pattern of extensive admixture in and around the contact zone. Nonetheless, the two species appear to have diverged > 4 Mya and might not even be sister taxa, suggesting that time of divergence alone might not be sufficient for the evolution of prezygotic reproductive barriers. Significantly more phenotypically red-fronted individuals had a P. c. extoni (yellow-fronted) genetic background than vice versa, suggesting possible asymmetry in mate preferences. Sexual selection may thus play a role in breaking down species barriers despite the extent of genetic divergence.en© 2019 The Linnean Society of London. This is the pre-peer reviewed version of the following article : 'Rampant introgressive hybridization in Pogoniulus tinkerbirds (Piciformes: Lybiidae) despite millions of years of divergence', Biological Journal of the Linnean Society, vol. 127, no. 1, pp. 125-142, 2019, doi : 10.1093/biolinnean/blz018. The definite version is available at : https://academic.oup.com/biolinnean.AsymmetryBarbetsContact zonesConvergenceInterbreedingIntrogressionPhylogeneticsPlumage colorationSpeciationSpecies interactionsSex-linked lociMitochondrial-DNAGene flowPopulation structureHybrid zoneSapsuckers (Sphyrapicus)Molecular markersSong divergenceOil dropletsYellow-fronted tinkerbird (Pogoniulus chrysoconus extoni)Red-fronted tinkerbird (Pogoniulus pusillus pusillus)Postprint Article