What Is Allelic Diversity?

MHC genes are associated with natural and sexual selection as MHC genes initiate immune responses and signaling against parasites and pathogens. The allelic diversity is a consequence of parasite-mediated balancing selection. Fish that seek MHC haplotypes are mostly favored by natural selection and have higher reproductive success. Results support the idea; females select partners that have intermediate MHC diversity and haplotypes since such males are bigger, fight pathogens better, provide the offspring with prenatal care, and retain good genes (immunized) for selection. Also, females display higher parasite load than males and female choosiness is affected by male density which results in extending genes and maintaining MHC polymorphism
through generations. In addition, coloration in males (redness) lowers reproductive success in offspring and thus force females to select males that have MHC haplotypes and resistance to parasites so that the offspring beat Darwinian fitness.