Digest: Chance and necessity shape introgression patterns across three replicate avian hybrid zones

Area of Science:

• Evolutionary biology
• Genomics
• Ornithology

Background:

• Predicting evolutionary trajectories is a key challenge in biology.
• Hybrid zones offer natural experiments to study evolutionary processes like introgression.
• Understanding the factors shaping introgression patterns is crucial for evolutionary insights.

Purpose of the Study:

• To assess the repeatability of introgression patterns between Lemon-rumped and Flame-rumped Tanagers.
• To investigate the role of selection versus chance in shaping genomic introgression.
• To identify specific genomic regions influencing introgression.

Main Methods:

• Utilized three replicate hybrid zones in the Western Andes of Colombia.
• Conducted genomic cline analyses to map introgression patterns.
• Differentiated between neutral and potentially selected introgression.

Main Results:

• Observed heterogeneous patterns of neutral introgression across the genome.
• Identified deterministic introgression at a specific locus on chromosome 22 associated with plumage.
• Demonstrated that introgression patterns are influenced by both chance and selection.

Conclusions:

• Evolutionary introgression is a complex process shaped by both contingency and deterministic selection.
• Selection can lead to predictable introgression patterns at functionally important loci, even amidst genomic randomness.
• These findings provide insights into the balance of chance and necessity in shaping biodiversity.