You study two populations of zebra skipper butterflies, one on the mainland and the other on a large island several hundred miles off the coast of Brazil. In the mainland population, males and females are nearly identical in size. By contrast, females are 1.2 times larger than males in the island population. How do you explain this fact? Pose a formal gender-specific hypothesis for this result.

What sorts of information would you need to test your idea? Could you select for changes in the body size ratio between males and females at both locations? What experimental design would you need to pull this off?