Stickleback fish exhibit variation in a morphological trait known as gill rakers. Fish with long gill rakers are very good at eating plankton, and fish with short gill rakers are good at eating deep-water invertebrates. However, fish with intermediate-length gill rakers are poor at eating either type of food. Fish that are better at consuming food have higher survival and reproduction rates than poorer consumers. Based on this information, what type of selection is likely acting on stickleback gill raker length?

Question

Quizplus · Accepted Answer

Stickleback fish with long gill rakers are good at consuming plankton and those with short gill rakers are good at eating deep-water invertebrates. Therefore, fish with intermediate-length gill rakers are poor at consuming either type of food, thereby incurring lower survival and reproduction rates. This situation indicates disruptive selection, which means that selection is favoring both extremes and not the intermediate trait.

Stickleback Fish Exhibit Variation in a Morphological Trait Known as Gill