Hybrid speciation leads to novel male secondary sexual ornamentation of an Amazonian bird

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 115; no. 2; pp. E218 - E225
• Main Authors: Barrera-Guzmán, Alfredo O., Aleixo, Alexandre, Shawkey, Matthew D., Weir, Jason T.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 09.01.2018
• Series: PNAS Plus
• Subjects: Biological Sciences; Birds; Coloration; Electron microscopy; Genetic markers; Genomes; Hybridization; Keratin; Morphology; PNAS Plus; Population structure; Reproductive isolation; River basins; Single-nucleotide polymorphism; Snow; Speciation; Species; Spectrophotometry; Thickening; Vertebrates; Amazon Basin; Lepidothrix vilasboasi; ornamentation; structural color; Amazon; hybrid speciation
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1717319115

Hybrid speciation is rare in vertebrates, and reproductive isolation arising from hybridization is infrequently demonstrated. Here, we present evidence supporting a hybrid-speciation event involving the genetic admixture of the snow-capped (Lepidothrix nattereri) and opal-crowned (Lepidothrix iris) manakins of the Amazon basin, leading to the formation of the hybrid species, the golden-crowned manakin (Lepidothrix vilasboasi). We used a genome-wide SNP dataset together with analysis of admixture, population structure, and coalescent modeling to demonstrate that the golden-crowned manakin is genetically an admixture of these species and does not represent a hybrid zone but instead formed through ancient genetic admixture. We used spectrophotometry to quantify the coloration of the species-specific male crown patches. Crown patches are highly reflective white (snow-capped manakin) or iridescent whitish-blue to pink (opal-crowned manakin) in parental species but are a much less reflective yellow in the hybrid species. The brilliant coloration of the parental species results from nanostructural organization of the keratin matrix feather barbs of the crown. However, using electron microscopy, we demonstrate that the structural organization of this matrix is different in the two parental species and that the hybrid species is intermediate. The intermediate nature of the crown barbs, resulting from past admixture appears to have rendered a duller structural coloration. To compensate for reduced brightness, selection apparently resulted in extensive thickening of the carotenoid-laden barb cortex, producing the yellow crown coloration. The evolution of this unique crown-color signal likely culminated in premating isolation of the hybrid species from both parental species.