How has parallel evolution manifested in stickleback armor traits across independent freshwater populations?

How has parallel evolution manifested in stickleback armor traits across independent freshwater populations?

• A. Random changes with no pattern
• B. Increase in plates in all freshwater populations
• C. Repeated, independent evolution toward reduced lateral plates across freshwater populations, often via similar genetic changes at EDA
• D. No evolution at all

Answer: (C)

Parallel evolution is being tested: different freshwater stickleback populations, evolving in similar environments, repeatedly arrive at the same adaptive solution—reduced lateral armor plates—despite doing so independently. In freshwater settings, carrying heavy armor is costly and offers little advantage, so natural selection favors fewer plates. Across many independent colonizations, this reduction in plates occurs repeatedly, and often involves similar genetic changes at the EDA gene, which regulates plate formation. This combination of a shared phenotype and a common genetic mechanism shows that evolution can follow predictable paths when environments exert similar pressures, which is precisely what this option captures.

Parallel evolution is being tested: different freshwater stickleback populations, evolving in similar environments, repeatedly arrive at the same adaptive solution—reduced lateral armor plates—despite doing so independently. In freshwater settings, carrying heavy armor is costly and offers little advantage, so natural selection favors fewer plates. Across many independent colonizations, this reduction in plates occurs repeatedly, and often involves similar genetic changes at the EDA gene, which regulates plate formation. This combination of a shared phenotype and a common genetic mechanism shows that evolution can follow predictable paths when environments exert similar pressures, which is precisely what this option captures.