How can you assess the heritability of plate number in sticklebacks?

• A. Heritability cannot be estimated in sticklebacks.
• B. Use parent-offspring regression or a half-sib design to estimate narrow-sense heritability (h^2) for plate number.
• C. Only twin studies can estimate heritability.
• D. Heritability is inferred from predator presence.

Answer: (B)

The key idea is measuring how much of the variation in plate number is due to additive genetic effects, using family-based data. In sticklebacks, you can estimate narrow-sense heritability (h^2) by designing crosses and comparing related individuals.

Parent-offspring regression works by measuring plate numbers in parents and their offspring and plotting offspring values against parental values. The slope of that relationship approximates h^2, because, on average, offspring phenotypes reflect the additive genetic contribution inherited from parents, once you’ve accounted for shared environment.

A half-sib design uses groups of offspring that share one parent but have different other parents. By analyzing how plate number varies among and within these half-sib groups, you can separate additive genetic variance from environmental variance. With controlled rearing conditions (a common garden) to reduce environmental noise, you can translate those variance components into an estimate of h^2.

In contrast, twin studies aren’t practical for sticklebacks, and inferring heritability solely from predator presence mixes environmental effects with genetics, which doesn’t yield a valid h^2 estimate.

So, using parent-offspring regression or a half-sib design provides direct, workable methods to quantify the additive genetic contribution to plate number in sticklebacks.