What is the most likely conclusion about Frog Lake sticklebacks relative to marine populations based on pelvic morphology?

• A. Frog Lake sticklebacks show no similarity to marine populations.
• B. Frog Lake sticklebacks are more similar to marine populations due to complete pelvises, implying similar selection pressures.
• C. Frog Lake sticklebacks have fewer spines than Bear Paw.
• D. Frog Lake sticklebacks are not juveniles.

Answer: (B)

Pelvic morphology in sticklebacks reflects how fish adapt to their environment. In many freshwater populations, the pelvic girdle is reduced or lost as a result of selection for streamlined bodies and different ecological pressures, while marine populations tend to keep a complete pelvis. If Frog Lake sticklebacks have a full, complete pelvis, that mirrors the pelvic condition of marine populations. This suggests they’re experiencing similar selection pressures to marine environments (or have retained the ancestral pelvic state), making them more similar to marine fish. The other ideas don’t fit with what pelvic shape typically signals about habitat-linked adaptation or ancestry.