Why is it significant that Eda explains a major proportion of plate variation across multiple populations?

Why is it significant that Eda explains a major proportion of plate variation across multiple populations?

• A. It demonstrates a repeatable genetic mechanism for adaptation and reduces the number of loci needed to explain the trait.
• B. It shows plates are not heritable.
• C. It indicates Eda is not evolving.
• D. It implies random drift is the main driver.

Answer: (A)

This shows a repeatable genetic mechanism for adaptation and a simple genetic architecture. Eda acts as a major gene that explains most of the variation in armor plates across many stickleback populations, especially in freshwater environments where plates tend to be reduced. When the same gene consistently accounts for a large share of the trait in independent populations, it indicates that evolution is using the same genetic pathway again and again to produce a similar phenotype. This makes the trait largely explainable by one locus with a strong effect, reducing the need to invoke many small-effect genes to account for the variation. That pattern also implies that selection can act quickly on standing variation at this locus, leading to parallel outcomes in different populations. The other options don’t fit because they imply no heritability, no evolution, or drift as the main driver, which wouldn’t produce the observed repeated, large-effect role for a single gene across populations.

This shows a repeatable genetic mechanism for adaptation and a simple genetic architecture. Eda acts as a major gene that explains most of the variation in armor plates across many stickleback populations, especially in freshwater environments where plates tend to be reduced. When the same gene consistently accounts for a large share of the trait in independent populations, it indicates that evolution is using the same genetic pathway again and again to produce a similar phenotype. This makes the trait largely explainable by one locus with a strong effect, reducing the need to invoke many small-effect genes to account for the variation.

That pattern also implies that selection can act quickly on standing variation at this locus, leading to parallel outcomes in different populations. The other options don’t fit because they imply no heritability, no evolution, or drift as the main driver, which wouldn’t produce the observed repeated, large-effect role for a single gene across populations.