Sex-Linked Differentiation in Commercially Exploited Fishes: Rethinking Population Structure in Dynamic Marine...

Area of Science:

• Marine genomics
• Population genetics
• Evolutionary biology

Background:

• Understanding genomic structure is key for predicting species' responses to environmental change, especially for commercially exploited marine species facing fishing pressure.
• Merluccius paradoxus, a commercially exploited fish, is expanding its range along the southern African coast, necessitating an investigation into its population structure and adaptive capacity.

Purpose of the Study:

• To investigate the drivers of genomic variation in Merluccius paradoxus.
• To challenge conventional assumptions of regional geographic population structure by examining sex-linked divergence.
• To assess the implications of genomic variation for species' adaptation and fisheries management.

Main Methods:

• Whole-genome sequencing of 37 Merluccius paradoxus individuals across their distribution.
• Analysis of genomic variation, focusing on autosomal regions and known sex-determining regions.
• Examination of nucleotide diversity, heterozygosity, and runs of homozygosity to infer population dynamics and selection.

Main Results:

• Sex-linked divergence, not geography, is the primary driver of genomic variation in Merluccius paradoxus.
• Genomic divergence is concentrated on autosomal regions (Chromosomes 1 and 2), not sex-determining regions (Chromosome 9).
• Males exhibit reduced nucleotide diversity and heterozygosity, suggesting recent selective sweeps or reduced effective population size, linked to genes involved in neuronal function, metabolism, and muscle development.

Conclusions:

• Sex-specific selection on autosomal genes influences genomic variation and potentially adaptive traits in Merluccius paradoxus.
• Differences in spatial distribution and genomic diversity between sexes suggest varied range dynamics and adaptive potential.
• Incorporating sex-linked genomic variation into conservation and fisheries management is crucial for transboundary species facing climate change and fishing pressures.