Males of the marine isopod Paracerceis sculpta come in three sizes: large alphas, medium betas, and small gammas. When the average fitness of each type was measured, researchers found that there were no statistically significant differences among the three types. The lack of a fitness difference between the three male phenotypes suggests that the behavioral differences among them are hereditary because
A) all phenotypes are 50 percent genetic and 50 percent environmental. B) the three phenotypes are three adaptations maintained because of their equal fitness effects. C) the three phenotypes appear to be three tactics controlled by a single conditional strategy. D) the three phenotypes have to be hereditary if they are to help the species improve over time.