Hardy–Weinberg principle applies only to
Hardy-Weinberg model assumes diploid organisms reproducing sexually with random fusion of male and female gametes, creating genotype frequencies from allele frequencies via binomial expansion (p plus q) squared. Haploid or clonal asexual populations lack formation of diploid genotypes from two independent gamete pools, so p squared, two pq, q squared framework does not apply appropriately. While allele frequencies in haploids still evolve via drift and selection, genotype equilibrium concept requires diploid sexual shuffling each generation. Thus principle is formulated specifically for diploid, sexually reproducing populations with Mendelian segregation.
Ref: Hartl & Clark, Principles of Population Genetics, Chapter 2: Scope of Hardy-Weinberg Model