Hybrid zone dynamics in buntings

Background

Questions

Implications

Team

Does sexual selection stabilize boundaries between species?

Hybrid zones are defined as areas where genetically differentiated groups of individuals meet, mate, and produce offspring of mixed ancestry. These zones have long been recognized as natural laboratories offering valuable insights into the phenotypes, and underlying genes, that prevent gene flow between emerging species. However, our understanding of the specific genetic regions responsible for early stages of reproductive isolation, and the role of sexual selection in shaping these barriers to gene flow over time, remains limited, especially in regions outside of well-studied temperate areas. To tackle these questions, we focus on a dynamic hybrid zone inhabited by two species of songbirds: the black-headed bunting (Emberiza melanocephala) and the red-headed bunting (E. bruniceps), exhibiting behavioral isolation by male plumage and female mate preference.

By employing whole-genome sequencing techniques and analyzing genotypic and phenotypic data from museum collections spanning approximately the last 25 generations of the hybrid zone, we aim to explore:

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 genetic differentiation over time?

Addressing these questions in the bunting hybrid zone we will provide general insights into whether colouration traits involved in sexual selection can act as reproductive barriers, effectively facilitating speciation. Additionally, by using museum collections we will test assumptions on hybrid zone stability that cannot be tested from extant populations alone.

Ricardo Pereira (SMNS), Niloofar Alaei Kakhki (SMNS), Reto Burri (Schweizer Vogelwarte), Holger Schielzeth (Uni Jena), Octavio M. Palacios-Gimenez (Uni Jena), Mansour Aliabadian (Ferdowsi University of Mashhad, Iran), Ali Gholamhosseini (Shiraz University, Iran)

Bunting-zone. Parental (left and right) and hybrid with intermediate (in the middle) phenotypes (Paludan, 1939). b) Species ranges based on © BirdLife International (blue: black-headed bunting, and yellow: red-headed bunting).

Fig. 1 Bunting-zone. Parental (left and right) and hybrid with intermediate (in the middle) phenotypes (Paludan, 1939). b) Species ranges based on © BirdLife International (blue: black-headed bunting, and yellow: red-headed bunting).