In sticklebacks, what does a repeatable pattern of adaptation involving the Eda gene indicate about armor reduction in freshwater stickleback populations?

In sticklebacks, what does a repeatable pattern of adaptation involving the Eda gene indicate about armor reduction in freshwater stickleback populations?

• A. Different genes must be responsible for armor changes in each freshwater population.
• B. Eda variation only occurs in marine populations and not freshwater.
• C. The same gene is repeatedly associated with reduced armor in independent freshwater populations, indicating parallel evolution.
• D. Armor reduction is entirely due to environmental factors with no genetic basis.

Answer: (C)

Armor reduction in freshwater sticklebacks is governed in part by a single gene, Eda, which controls how many bony plates develop along the body. When the same gene shows the same kind of variation in multiple, independently derived freshwater populations, it reveals parallel evolution: separate groups facing similar ecological pressures repeatedly arrive at the same genetic solution. This pattern means the change is heritable and driven by selection on that gene, rather than being caused by environment alone or requiring different genes in each population. It also contradicts ideas that Eda variation only exists in marine fish or that armor changes must come from entirely different genetic routes across populations.

Armor reduction in freshwater sticklebacks is governed in part by a single gene, Eda, which controls how many bony plates develop along the body. When the same gene shows the same kind of variation in multiple, independently derived freshwater populations, it reveals parallel evolution: separate groups facing similar ecological pressures repeatedly arrive at the same genetic solution. This pattern means the change is heritable and driven by selection on that gene, rather than being caused by environment alone or requiring different genes in each population. It also contradicts ideas that Eda variation only exists in marine fish or that armor changes must come from entirely different genetic routes across populations.