This family contains birds known as Buntings in the Old World.
Yellowhammer (E. citronella) and Pine Bunting (E. leucocephalos) hybridize in Russia (Panov, Rubtsov & Monzikov, 2003a; Panov, Roubtsov & Monzikov, 2003b). Genetic analyses showed low divergence in mtDNA compared to nDNA, which could be attributed to recent divergence or introgression (Irwin, Rubtsov & Panov, 2009). The latter hypothesis (introgression) was indicated as more likely by a phylogenetic analysis which showed that these species are not sister species (Rubtsov & Opaev, 2012). Despite large morphological differences, both species produce indistinguishable territorial songs (Tietze, Wassmann & Martens, 2012).
A study on the vocal variation among three subspecies of the Reed Bunting (E. schoeniclus) uncovered a “hybrid zone” between E. s. schoeniclus and two southern subspecies (E. s. intermedia and E. s. witherbyi). This hybrid zone has not been confirmed by morphological or genetic data (Matessi, Pilastro & Marin, 2000). Playback experiments showed that different responses to songs from different subspecies: witherbyi and – to some extent lusitanica – males largely ignored schoeniclus songs, while schoeniclus males did not discriminate the songs of the different subspecies, reacting strongly to all. These results suggest some degree of premating isolation (de Oliveira Gordinho et al., 2016).
A phylogenetic analysis of “African brown buntings” lacked reciprocal monophyly, possibly due to incomplete lineage sorting. The analysis revealed one hybrid specimen in the dataset (Olsson, Yosef & Alstrom, 2013). House Bunting (E. sahari) and Striolated Bunting (E. striolata) are considered to be distinct species. A phylogeographic study across the Saharo-Arabian range of these species revealed incongruence between mtDNA and morphology in certain populations. This pattern can be explained by incomplete lineage sorting or introgressive hybridization (Schweizer et al., 2017).
Gholamhosseini et al. (2017) revisited a hybrid zone between Black-headed Bunting (Emberiza melanocephala) and Red-headed Bunting (E. bruniceps) in northern Iran that has been studied by Paludan (1940) and Haffer (1977). The hybrid zone has expanded westward by approximately 170 km. From a climatic point of view, the Black-headed Bunting could occur farther to the east, but it doesn’t. Probably, it is out-competed by the Red-headed Bunting which might be expanding eastward due to land use changes by humans (i.e. deforestation and extension of agriculture).
de Oliveira Gordinho, L., Hasselquist, D. & Neto, J.M. (2016) Asymmetric song recognition between recently diverged subspecies of reed bunting. Behavioural Ecology 5(1), 1413-1423.
Gholamhosseini, A., Aliabadian, M., Darvish, J., Töpfer, T. & Sætre, G.-P. (2017). An Expanding Hybrid Zone between Black-Headed and Red-Headed Buntings in Northern Iran. Ardea 105, 27-36.
Irwin, D. E., Rubtsov, A. S. & Panov, E. N. (2009). Mitochondrial introgression and replacement between yellowhammers (Emberiza citrinella) and pine buntings (Emberiza leucocephalos) (Aves: Passeriformes). Biological Journal of the Linnean Society 98, 422-438.
Matessi, G., Pilastro, A. & Marin, G. (2000). Variation in quantitative properties of song among European populations of reed bunting (Emberiza schoeniclus) with respect to bill morphology. Canadian Journal of Zoology-Revue Canadienne De Zoologie 78, 428-437.
Olsson, U., Yosef, R. & Alstrom, P. (2013). Assessment of species limits in African ‘brown buntings’ (Emberiza, Passeriformes) based on mitochondrial and nuclear sequence data. Ibis 155, 534-543.
Panov, E., Rubtsov, A. & Monzikov, D. (2003a). Relationships between Two Species of Buntings (Emberiza citrinella and E. leucocephalos) Hybridizing in the Zones of Overlap of Their Ranges. Zool. Zh 82, 470-484.
Panov, E. N., Roubtsov, A. S. & Monzikov, D. G. (2003b). Hybridization between yellowhammer and pine bunting in Russia. Dutch Birding 25, 17-31.
Rubtsov, A. S. & Opaev, A. S. (2012). Phylogeny reconstruction of the yellowhammer (Emberiza citrinella) and pine bunting (Emberiza leucocephala) based on song and morphological characters. Biology Bulletin 39, 715-728.
Schweizer, M., H. Shirihai, H. Schmaljohann and G. M. Kirwan (2017). Phylogeography of the House Bunting complex: discordance between species limits and genetic markers. Journal of Ornithology 159, 47-61.
Tietze, D. T., Wassmann, C. & Martens, J. (2012). Territorial song does not isolate Yellowhammers (Emberiza citrinella) from Pine Buntings (E. leucocephalos). Vertebrate Zoology 62, 113-122.