A Comparative Study of Fitness Landscapes: Testing Competitive Disruptive Selection in Sticklebacks

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Even in ecology, "it pays to be different". Animals that eat the same food as their fellows experience strong competition, while animals that use different resources may avoid competition. As a result, in a given population individuals with average morphologies may be less fit than individuals with rare morphologies; this is known as 'disruptive selection'. In previous work, Dr. Bolnick confirmed that competition can cause disruptive selection in a species of fish (sticklebacks). The goal of the current project is to determine whether this disruptive selection is common. Dr. Bolnick will measure natural selection in many populations of sticklebacks by capturing fish from 20 lakes, comparing their growth rate and reproductive potential to their morphology and diet. The frequency of disruptive selection is important because, unlike other types of natural selection, it can enhance genetic diversity. This project will be the first test of whether this diversity-enhancing process is common in natural populations. The result may have practical significance: if genetic diversity is maintained by competition, the low population densities of many threatened species might undermine their genetic variability. The project will provide future high-school science teachers with research experience, and be used for public education about evolution.