Final answer:
Stabilizing selection and frequency-dependent selection are two forms of selection that maintain genetic diversity in a population by respectively favoring average phenotypes and either common or rare phenotypes, while sexual selection also contributes through mate attraction traits.
Step-by-step explanation:
Two forms of selection that could maintain genetic variation within a population are stabilizing selection and frequency-dependent selection. Stabilizing selection favors an average phenotype, selecting against extreme variants within a population. This can be observed in mouse populations where natural selection favors mice whose fur color closely matches the forest floor for camouflage, reducing predation. In contrast, frequency-dependent selection can maintain genetic diversity by favoring phenotypes that are either common or rare, depending on whether it is positive or negative frequency-dependent selection. Positive frequency-dependent selection favors common phenotypes, while negative frequency-dependent selection gives an advantage to rarer phenotypes, thus maintaining genetic variance within the population.
Another important aspect is sexual selection, which can also contribute to the maintenance of genetic diversity. This form of selection is based on the ability of individuals to attract mates and can lead to a diversity of traits within the population. For example, the good genes hypothesis posits that individuals with impressive ornaments, which may indicate a better ability to fight disease or a more efficient metabolism, will be more successful at attracting mates and thus passing on their genes.