Genome-wide SNPs confirm plumage polymorphism and hybridisation within a Cyornis flycatcher species complex

Morphology has been a leading taxonomic guiding light to systematists for the last couple of hundred years. However, the genetic and - more recently - genomic revolution have produced numerous demonstrations of erroneous classifications that were based on labile morphological traits. We used thousands of genome-wide markers to shed light on evolutionary dynamics in a confusing and taxonomically obscure group of Asian Cyornis flycatchers. Using genomic data, we corroborated recent findings based on three mitochrondrial and five nuclear genes that the two taxa hainanus and klossi which were previously treated as separate species (Cyornis hainanus and Cyornis rubeculoides klossi, respectively) are genomically homogeneous and form a single species, C. hainanus. We also uncovered a novel case of interbreeding between C. hainanus and a non-sister species, C. glaucicomans, illustrating these flycatchers' ability to hybridise in marginal situations even after substantial times of divergence. Our study illustrates how genome-wide loci can shed light on complicated taxonomic problems, resulting in a better integration of phenotypic and genotypic data.

Automated summary

Morphology has long been a reliable tool for taxonomic classification, but recent genetic and genomic advancements have shown that it can lead to erroneous classifications. In our study on Asian Cyornis flycatchers, we used thousands of genomic markers to confirm that two previously recognized species are actually a single species, and we also discovered interbreeding between two different species, highlighting their ability to hybridize even after long periods of divergence. This research demonstrates the importance of incorporating genomic data into taxonomic studies for a more comprehensive understanding of species relationships.