QTL mapping is used for in stickleback studies?

• A. To estimate mutation rates across populations
• B. To locate genomic regions associated with variation in adaptive traits like armor, spines, or body shape
• C. To determine historical population size
• D. To analyze gene flow between habitats

Answer: (B)

QTL mapping is about linking differences in a measurable trait to specific regions of the genome. In sticklebacks, researchers look at traits that vary between populations—like the number of armor plates, spine length, or overall body shape—and genotype many markers across the genome in offspring from crosses between divergent populations. By seeing which genomic regions co-segregate with the trait differences, scientists identify quantitative trait loci that contribute to that variation. This approach directly targets the genetic loci underlying adaptive traits in sticklebacks, helping map the genomic architecture of features shaped by natural selection.

The other ideas aren’t what this method does: estimating mutation rates, inferring historical population size, or analyzing gene flow between habitats rely on population-genetics approaches that focus on demographic history and migration rather than linking specific trait variation to particular genomic regions.