Trans-oceanic genomic divergence of Atlantic cod ecotypes is associated with large inversions

Area of Science:

• Evolutionary genetics
• Population genomics
• Speciation research

Background:

• Chromosomal rearrangements, specifically inversions, are key to maintaining genetic diversity and driving speciation.
• Large inversions in Atlantic cod (Gadus morhua) are linked to genomic differentiation between migratory and nonmigratory ecotypes in the Northeast Atlantic.

Purpose of the Study:

• To investigate the role of inversions in ecotype divergence in Atlantic cod populations across the Atlantic Ocean.
• To determine the evolutionary origin and persistence of these inversions.

Main Methods:

• Comparative genomics analysis of Atlantic cod populations.
• Identification and characterization of large chromosomal inversions.
• Analysis of genomic divergence patterns between ecotypes.

Main Results:

• The same large genomic regions with inversions show elevated divergence in both Northeast and Northwest Atlantic cod populations.
• These inversions predate the trans-Atlantic separation of cod populations (>100,000 years ago).
• Evidence suggests selection maintains these inversions, potentially linked to complex traits and migratory behavior.

Conclusions:

• Large chromosomal inversions are a conserved mechanism for ecotype divergence in Atlantic cod on both sides of the Atlantic.
• Migratory behavior appears to be a derived trait from more stationary ancestral ecotypes.
• These findings highlight the role of inversions in maintaining genomic divergence and potentially driving speciation in this species.