Three-spined stickleback fish (Gasterosteus aculeatus) show substantial heritable variation in gill-raker length related to differences in their diets. Longer gill rakers appear to function better for capturing open-water prey, while shorter gill rakers function better for capturing shallow-water prey. Which of the following types of selection is most likely to be found in a large lake (open water in the middle and shallow water around the sides) with a high density of these fish?

Question

Quizplus · Accepted Answer

In a large lake with both open water and shallow water areas, there are likely to be different prey types available in each area. This creates two different selective pressures on the three-spined stickleback fish population: one for longer gill rakers for capturing open-water prey and one for shorter gill rakers for capturing shallow-water prey. This creates a situation where individuals with intermediate gill-raker length are selected against, leading to disruptive selection.

Three-Spined Stickleback Fish (Gasterosteus Aculeatus) Show Substantial Heritable Variation in Gill-Raker