Phylogeny reconstruction of the yellowhammer (Emberiza citrinella) and pine bunting (Emberiza leucocephala) based on song and morphological characters

Abstract

The yellowhammer and pine bunting represent a quite rare case of mass hybridization in a broad secondary contact zone. Previously, it was shown that the two forms did not differ by mitochondrial DNA (Irwin et al., 2009). This result allowed suggesting either a very close evolutionary relationship between these species or a consequence of borrowing the mitochondrial genome due to long-term hybridization. An attempt to reconstruct the phylogeny of these species was made on the basis of cluster analysis performed relative to the song characters and morphological features (male coloration and morphometric characters). The geographical variability of songs in yellowhammers and pine buntings was also investigated. The cladistic analysis included another 5 closely related bunting species: cirl (E. cirlus), chestnut-breasted (E. stewarti), ortolan (E. hortulana), grey-necked (E. buchanani), and Cretzschmar’s bunting (E. caesia). Based on the results of our analysis, the yellowhammer and pine bunting show no sister relationship. They compose the smallest clusters: one with the cirl bunting and the other one with the chestnut-breasted bunting. Thus, in this paper we attempt to prove the hypothesis of a high divergence level between the species and mtDNA introgression from the pine bunting into the yellowhammer following long term hybridization. The analysis of song dialects agrees with the assumption that there existed an ancient hybrid zone between the yellowhammer and the pine bunting in Europe.