What is the term for the bias toward phenotypically different mates?

The correct term for the bias toward phenotypically different mates is negative assortative mating. This phenomenon occurs when individuals preferentially choose mates that have different phenotypic traits from themselves, which can enhance genetic diversity in a population. By selecting partners that are different in some significant way, such as size, coloration, or behavior, organisms are able to increase the likelihood of attracting genetically diverse offspring, which can improve adaptability and resilience.

In contrast, positive assortative mating is defined by individuals selecting mates that are similar in phenotype, which tends to decrease genetic diversity. Random mating does not involve any preferences regarding phenotype; mates are selected without regard to their traits. Inbreeding refers to mating between closely related individuals and often leads to a reduction in genetic variation and can result in increased expression of deleterious traits. Thus, negative assortative mating is specifically characterized by the preference for mates that exhibit distinct phenotypic differences, promoting diversity within the gene pool.