BUNTING-ZONE: a natural laboratory to understand how colour pattern maintains species boundaries in birds

• Applicants: Dr. Niloofar Alaei Kakhki; Ricardo Pereira, Ph.D.
• Subject Area: Systematics and Morphology (Zoology)
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 548007760

Hybrid zones are defined as areas where genetically differentiated groups of individuals meet, mate, and produce offspring of mixed ancestry. For decades, hybrid zones have been considered as natural laboratories that provide direct insights into the traits and genes underlying barriers to gene flow between incipient species over time. However, our understanding of the genomic regions underlying the initial stages of reproductive isolation and the extent to which selection can effectively reduce gene flow over time facilitating species formation remain limited to few well-studied organisms in temperate parts of the globe. Addressing these longstanding questions requires studying hybrid zones where known phenotypes are associated with reproductive isolation, where those phenotypes can be linked to genotypes, and where temporal sampling over several generations is available. Here, we address these questions using a moving hybrid zone between two songbirds – black-headed bunting Emberiza melanocephala and red-headed bunting E. bruniceps – where species are hypothesised to be behaviourally isolated due to an association between male plumage and female preference. By integrating whole genome sequencing methods with genotypic and phenotypic studies of museum collections spanning the last ~25 generations of the hybrid zone, we will assess: 1. How heterogeneous is the genomic landscape of differentiation? 2. Which genomic regions are associated with the plumage traits? 3. Does selection in those regions maintain local genetic differentiation over time in the face of gene flow? Addressing these questions in the bunting hybrid zone will integrate in the same system methods that allow understanding how colouration traits involved in reproductive isolation evolve and result in permeable barriers to gene flow in a region of the world with the highest concentration of contact zones. Additionally, by using museum collections we will test assumptions on hybrid zone stability that cannot be tested from extant populations alone.

• DFG Programme: Research Grants