Who we study:
The white wagtail subspecies complex
The white wagtail (Motacilla alba) is a widespread passerine bird, with nine subspecies commonly recognized by systematists based on plumage differences. Previous studies revealed that the striking phenotypic variation in this radiation is associated with extremely little genetic differentiation. This pattern is an interesting phenomenon for evolutionary biologists—white wagtail subspecies likely represent the very early stages of the speciation process and provide an opportunity to investigate the mechanisms that promote biological diversification.
Siberian hybrid zone
Two subspecies of the white wagtail, M. a. alba and M. a. personata, have a narrow hybrid zone in the Altai-Sayan region of Siberia. Interestingly, head plumage differences change abruptly - over a span of 100 kilometers - across this hybrid zone, whereas all other traits and genetic ancestry demonstrate a more gradual transition. Furthermore, wagtails mate assortatively with respect to head plumage, in other words "pure" personata and alba form pairs. These findings suggest that head plumage is an important signaling trait involved in, or potentially even promoting, divergence and speciation in wagtails.
What we study:
We use whole-genome sequences and many tens of individuals sampled across the alba and personata hybrid zone (and remote populations) to dissect the genetic architecture of head plumage patterning. The approach we use is known as admixture mapping, and it takes advantage of the intermediate phenotypes and genotypes that occur in the hybrid zone. We also use extensive genomic datasets to reconstruct the history of hybridization and population dynamics to better understand how selection and gene flow contributed to the contemporary patterns we observe.
Semenov G, Linck E, Enbody E, Harris R, Khaydarov D, Alström P, Andersson L, Taylor SA. 2021. Asymmetric introgression reveals the genetic architecture of a plumage trait. Nature Communications 12, Article number: 1019. https://www.nature.com/articles/s41467-021-21340-y