Search for: All records

Genomic data can provide valuable insights into the evolutionary history of rapidly diversifying groups and the genetic basis of phenotypic differences among lineages. We used whole-genome sequencing of the warbler genus Myioborus to investigate dynamics of its recent diversification in Neotropical mountains. We found that mitochondrial and UCE phylogenies are mostly, but not fully, concordant, and we found phylogenetic support for a pattern of north-to-south and low-to-high elevation colonization in the genus. Within the ornatus-melanocephalus complex, which showed topological incongruence between our phylogenies, we found that genetic structure generally coincides with geographic variation in plumage, although three subspecies with striking plumage differences exhibit low mitochondrial divergence. The hybridizing taxa M. o. chrysops and M. m. bairdi show very shallow genomic differentiation, with marked peaks of divergence. Most of these are shared with other parulid warbler pairs, pointing to broad genomic features, like recombination rate, as the processes shaping these regions. However, other highly differentiated regions were unique to Myioborus, including one containing the gene CCDC91, which is associated with melanin-based plumage differences in several other birds. Lastly, we found higher levels of differentiation on the Z chromosome relative to autosomes, including two putative chromosomal inversions. Together, these results highlight the interplay of deep ancestral divergence, recent hybridization, and shared genomic architecture in shaping the evolution of phenotypic and genomic diversity within Myioborus. 

In a hybrid zone between two tropical lekking birds, yellow male plumage of one species has introgressed asymmetrically replacing white plumage of another via sexual selection. Here, we present a detailed analysis of the plumage trait to uncover its physical and genetic bases and trace its evolutionary history. We determine that the carotenoid lutein underlies the yellow phenotype and describe microstructural feather features likely to enhance color appearance. These same features reduce predicted water shedding capacity of feathers, a potential liability in the tropics. Through genome-scale DNA sequencing of hybrids and each species in the genus, we identifyBCO2as the major gene responsible for the color polymorphism. TheBCO2gene tree and genome-wide allele frequency patterns suggest that carotenoid-pigmented collars initially arose in a third species and reached the hybrid zone through historical gene flow. Complex interplay between sexual selection and hybridization has thus shaped phenotypes of these species, where conspicuous sexual traits are key to male reproductive success.