Which approach is commonly used in genome-wide scans to identify regions under selection when comparing marine and freshwater sticklebacks?

Which approach is commonly used in genome-wide scans to identify regions under selection when comparing marine and freshwater sticklebacks?

• A. By measuring predator density directly in lakes.
• B. By analyzing SNP data to identify outlier FST, reduced diversity, and signals like extended haplotype homozygosity.
• C. By comparing phenotypic measurements only.
• D. By sequencing only mitochondrial DNA.

Answer: (B)

Genome-wide scans for selection look for patterns across many genetic sites that reveal how populations have adapted to different environments. When you analyze SNP data from marine and freshwater sticklebacks, you can measure how differentiated each locus is between the two groups using FST; loci with unusually high differentiation are prime candidates for having been pushed by divergent selection. At the same time, regions around a beneficial allele often show less genetic diversity than neutral parts of the genome, because the advantageous variant and nearby linked variants sweep to high frequency together. Signals like extended haplotype homozygosity capture this recent hitchhiking effect, where a long, shared haplotype surrounding a favorable allele remains intact before recombination can break it up. Combining these genome-wide signals across many SNPs lets researchers map regions under selection that differentiate marine from freshwater sticklebacks. In contrast, ecological measurements alone, phenotypic comparisons only, or sequencing only mitochondrial DNA don’t provide the comprehensive nuclear-genome signals needed to identify these selected regions.

Genome-wide scans for selection look for patterns across many genetic sites that reveal how populations have adapted to different environments. When you analyze SNP data from marine and freshwater sticklebacks, you can measure how differentiated each locus is between the two groups using FST; loci with unusually high differentiation are prime candidates for having been pushed by divergent selection. At the same time, regions around a beneficial allele often show less genetic diversity than neutral parts of the genome, because the advantageous variant and nearby linked variants sweep to high frequency together. Signals like extended haplotype homozygosity capture this recent hitchhiking effect, where a long, shared haplotype surrounding a favorable allele remains intact before recombination can break it up. Combining these genome-wide signals across many SNPs lets researchers map regions under selection that differentiate marine from freshwater sticklebacks. In contrast, ecological measurements alone, phenotypic comparisons only, or sequencing only mitochondrial DNA don’t provide the comprehensive nuclear-genome signals needed to identify these selected regions.