Difference between fis and gis in population genetics
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Answer:
Genetic diversity is the total amount of variation in a population (or among populations). Population structure is how those variants are distributed. For example, if you use the simple case of two alleles in a population, they may be at 0.5 Heterozygosity (which is one measure of diversity), or 50% frequency of each allele. But one allele may be fixed in one population, the two at 50/50 frequency in another, and fixed for the alternate allele in yet another. Assuming those three populations were each the same size the overall frequency of each allele would still be 50%, but the populations themselves are structured. There's a number of different ways of measuring structure, but the most common way is using hierarchical F-statistics.
The minimum number of samples to detect structure will depend on the amount of variation in the populations you're measuring, the type of data, and the specific measure of structure you're using, but a good general rule of thumb is 15-30 samples for diploid data. Obviously larger samples are more reliable, but over 30-40 the increase in accuracy will generally start to plateau. The only way to be completely sure is via modeling or doing an extinction curve..