Inferring past demography and genetic adaptation in Spain using the GCAT cohort

Area of Science:

• Population Genetics
• Human Evolution
• Genomics

Background:

• The Iberian Peninsula's unique geography may have influenced distinct genetic adaptations.
• Previous studies suggest varied gene flow patterns in Europe.

Purpose of the Study:

• To quantify historical gene flow into Spain.
• To identify signatures of positive selection in the Spanish population.
• To discover novel adaptive genes and genomic regions.

Main Methods:

• Analysis of 704 whole-genome sequences from the GCAT reference panel.
• Quantification of gene flow from historical sources.
• Identification of positive selection signatures using local ancestry deviation analysis.

Main Results:

• No clear evidence for 16th-century French admixture was found.
• Significant North African admixture signals linked to historical Muslim and Reconquista periods were detected.
• Novel candidate genes (UBL7, SMYD1, VAC14, FDFT1) associated with immunity and diet showed positive selection.
• The MHCIII region exhibited post-admixture selection following Steppe ancestry admixture.

Conclusions:

• Spanish population genetics are shaped by North African admixture and distinct selective pressures.
• New genes involved in immunity and diet have undergone adaptive evolution in Spain.
• Genomic regions like MHCIII show evidence of selection after major admixture events.