A migratory divide spanning two continents is associated with genomic and ecological divergence

Area of Science:

• Evolutionary Biology
• Ornithology
• Ecology

Background:

• Migratory divides are crucial contact zones for studying reproductive isolation.
• Understanding population structure and migratory strategies is key to evolutionary divergence.

Purpose of the Study:

• Investigate migratory timing and routes of barn swallow subspecies in China.
• Examine the role of migration in maintaining reproductive isolation across a hybrid zone.

Main Methods:

• Utilized light-level geolocators, genomic sequencing, and stable isotope analysis.
• Compared migratory behavior and genetic differentiation between barn swallow subspecies west and east of a hybrid zone.

Main Results:

• Subspecies west (H. r. rustica) migrated to eastern Africa; subspecies east (H. r. gutturalis) migrated to southern India.
• Divergent migratory routes, influenced by the Karakoram Range, led to a 3-week difference in breeding ground arrival.
• Isotope values differed, correlating with migratory destinations and subspecies ancestry.

Conclusions:

• Assortative mating by arrival time or selection against intermediate hybrids likely maintains reproductive isolation.
• Geographic barriers may have driven migratory pattern diversification in Asian avifauna.