4.17—Measuring biodiversity and heterozygosity

Genetic diversity can be estimated from the proportion of individuals that are heterozygous: heterozygosity index = number of heterozygotes ÷ total number of individuals.

Count the heterozygous individuals for the chosen gene or sample, divide by the full sample size and compare like with like. A larger value means more individuals carry two different alleles at that locus; it is not a complete census of every gene.

If 18 of 60 individuals are heterozygous, the index is 18/60 = 0.30. Comparing two populations is meaningful only when the locus, sample method and population context are comparable.

Heterozygosity is a proportion, not a percentage unless multiplied by 100. A single locus or small sample can miss genetic diversity elsewhere and can be biased by sampling.