The grey partridge population has experienced significant declines across Europe, largely due to agricultural intensification and loss of habitat, leading to conservation actions such as Red-listing in the UK and hunting bans in Greece. The genetics of Balkan and Scottish populations remain largely unexplored; genetic analyses are essential to evaluate the impact of past restocking efforts on wild populations, as breeding between released and wild-living partridges may complicate recovery efforts. In this study, we sample wild and farmed individuals of grey partridge from the Balkans (Greece, North Macedonia) and the United Kingdom (UK) and employ 2300 SNPs, eight microsatellites and two mitochondrial markers to investigate the genetic structure and diversity of their populations and the impact of past restocking activities. We reveal a clear distinction between two clades, an Eastern and a Western, as in previous studies, with wild birds from Greece and the UK classified to each clade respectively. However, birds from North Macedonia belonged to either clade, suggesting a contact zone between the two or a genetic legacy of past restocking practices. The captive stock in Greece and the UK is clearly of Western origin, with minor introgression of the Eastern clade being detected. Finally, an informative SNP marker panel is presented that accurately assigns each individual to either the Eastern or Western clade and will serve as a valuable tool for monitoring population structure, guiding conservation efforts, and assessing the impact of restocking activities on grey partridge populations.

Genome scans offer a comprehensive method to explore genome-wide variation associated with traits under study. However, connecting individual genes to broader functional groupings and pathways is often challenging, yet crucial for understanding the evolutionary mechanisms underlying these traits. This task is particularly relevant for multi-trait processes such as domestication, which are influenced by complex interactions between numerous genetic and non-genetic factors, including epigenetic regulation. As various traits within the broader spectrum of domestication are selected in concert over time, this process offers an opportunity to identify broader functional overlaps and understand the integrated genetic architecture underlying these traits. In this study, we analyzed approximately 600,000 SNPs from a Pool-Seq experiment comparing eight natural-origin and 12 farmed populations of European seabass in the Mediterranean Sea region. We implemented two genome scan approaches and focused on genomic regions supported by both methods, resulting in the identification of 96 candidate genes, including nine CpG islands, highlighting potential epigenetic influences. Many of these genes and CpG islands are in linkage groups previously associated with domestication-related traits. The most significantly overrepresented molecular function was ‘oxidoreductase activity’. Furthermore, a dense network of interactions was identified, connecting 22 of the candidate genes. Within this network, the most significantly enriched pathways and central genes were involved in ‘chromatin organization’, highlighting another potential epigenetic mechanism. Altogether, our findings underscore the utility of interactome-assisted pathway analysis in elucidating the genomic architecture of polygenic traits and suggest that epigenetic regulation may play a crucial role in the domestication of European seabass.

Genome scans offer a comprehensive method to explore genome-wide variation associated with traits under study. However, connecting individual genes to broader functional groupings and pathways is often challenging, yet crucial for understanding the evolutionary mechanisms underlying these traits. This task is particularly relevant for multi-trait processes such as domestication, which are influenced by complex interactions between numerous genetic and non-genetic factors, including epigenetic regulation. As various traits within the broader spectrum of domestication are selected in concert over time, this process offers an opportunity to identify broader functional overlaps and understand the integrated genetic architecture underlying these traits. In this study, we analyzed approximately 600,000 SNPs from a Pool-Seq experiment comparing eight natural-origin and 12 farmed populations of European seabass in the Mediterranean Sea region. We implemented two genome scan approaches and focused on genomic regions supported by both methods, resulting in the identification of 96 candidate genes, including nine CpG islands, highlighting potential epigenetic influences. Many of these genes and CpG islands are in linkage groups previously associated with domestication-related traits. The most significantly overrepresented molecular function was ‘oxidoreductase activity’. Furthermore, a dense network of interactions was identified, connecting 22 of the candidate genes. Within this network, the most significantly enriched pathways and central genes were involved in ‘chromatin organization’, highlighting another potential epigenetic mechanism. Altogether, our findings underscore the utility of interactome-assisted pathway analysis in elucidating the genomic architecture of polygenic traits and suggest that epigenetic regulation may play a crucial role in the domestication of European seabass.

Gene function conservation is crucial in molecular ecology, especially for key traits like growth and maturation in teleost fish. The vgll3 and six6 genes are known to influence age-at-maturity in Atlantic salmon, but their impact on other fish species is poorly understood. Here, we investigated the association of vgll3 and six6 in the domestication of gilthead seabream and European seabass, both undergoing selective breeding for growth-related traits in the Mediterranean. We analysed two different sets of samples using two different genotyping approaches. The first dataset comprised farmed and wild populations from Greece, genotyped for SNPs within the genomic range of the two genes (“gene-level genotyping”). The second dataset examined 300k to 600k SNPs located in the chromosomes of the two genes, derived from a meta-analysis of a Pool-Seq experiment involving farmed and wild populations distributed widely across the Mediterranean (“chromosome-level genotyping”). The gene-level analysis revealed a significant effect of domestication on both genes in each species. This finding was partially supported by the chromosome-level analysis, identifying highly differentiated regions associated with domestication at varying distances from the candidate genes. Noteworthy genomic features were found, such as a CpG island in gilthead seabream and novel candidate genes in European seabream, warranting further investigation. These findings support a putative role of vgll3 and six6 in the maturation and growth of gilthead seabream and European seabass, emphasizing the need for further research on their conserved function.