Inversions Dominate Evolution in the European Sardine (Sardina pilchardus) Amid Strong Gene Flow

Area of Science:

• Genomics
• Evolutionary Biology
• Population Genetics

Background:

• Inversions are known to impact adaptation, but their genome-wide effects across species are not well understood.
• The European sardine (Sardina pilchardus) is an r-selected species with distinct Atlantic and Mediterranean populations.

Purpose of the Study:

• To investigate the role of inversions in the population genomics and adaptation of Sardina pilchardus.
• To understand how inversions shape genetic diversity and population structure in a species with high gene flow.

Main Methods:

• Whole-genome sequencing and demographic modeling were employed.
• Millions of single nucleotide polymorphisms (SNPs) were analyzed across 34 populations.
• Genomic scans identified outlier regions associated with large inversions.

Main Results:

• Several large inversions (29-52 Mbp) were identified, collectively spanning over half the genome.
• Inversions showed significant allele frequency differences between Atlantic and Mediterranean populations, correlating with life-history traits.
• Inversion frequencies varied geographically, aligning with environmental factors and reducing gene flow between adjacent populations.

Conclusions:

• Large inversions are under selection and play a crucial role in shaping genome-wide genetic diversity and population structure in Sardina pilchardus.
• These findings highlight the capacity of inversions to drive local adaptation despite widespread gene flow.
• The study provides insights for the management and conservation of this commercially important fish stock under climate change.