Final answer:
The effective population size equation in the presence of sexual selection would be influenced by mating patterns and variance in reproductive success, diverging from the traditional Hardy-Weinberg equilibrium due to the selective pressures altering allele frequencies and genetic diversity.
Step-by-step explanation:
The question asks about the effective population size equation when sexual selection is present. Sexual selection can lead to significant differences between the sexes in a species, often in size, strength, or adornment—traits that influence mate choice and success. This form of selection can cause skews in the reproductive success among members of a population, especially males, where a few may have most of the matings while others have few or none. Such skew in mating causes a departure from the equal reproductive opportunity assumed in the Hardy-Weinberg equilibrium, thereby affecting the effective population size.
Hardy-Weinberg principle assumes no selection among other requirements for equilibrium. When considering sexual selection, traditional Hardy-Weinberg computations of genotype and allele frequencies do not hold, as sexual selection violates the no selection condition of Hardy-Weinberg equilibrium. There may not be a straightforward equation for effective population size in the presence of sexual selection, as it would largely depend on the specific mating patterns, variance in reproductive success, and the intensity and mechanism of sexual selection. This mechanism can significantly alter allele frequencies and the genetic structure of populations, contributing to evolution. It is essential to understand that sexual selection, by favoring certain traits, reduces genetic diversity for those traits while potentially increasing overall genetic variance within the population due to negative frequency-dependent selection.