Аннотация
Population structure can be described by genotypic-correlation coefficients between groups of individuals, the most basic
of which are the pairwise relatedness coefficients between any two individuals. There are nine pairwise relatedness coefficients in the
most general model, and we show that these can be reduced to seven coefficients for biallelic loci. Although all nine coefficients can be
estimated from pedigrees, six coefficients have been beyond empirical reach. We provide a numerical optimization procedure that
estimates all seven reduced coefficients from population-genomic data. Simulations show that the procedure is nearly unbiased, even
at 33 coverage, and errors in five of the seven coefficients are statistically uncorrelated. The remaining two coefficients have a negative
correlation of errors, but their sum provides an unbiased assessment of the overall correlation of heterozygosity between two
individuals. Application of these new methods to four populations of the freshwater crustacean Daphnia pulex reveal the occurrence
of half siblings in our samples, as well as a number of identical individuals that are likely obligately asexual clone mates. Statistically significant
negative estimates of these pairwise relatedness coefficients, including inbreeding coefficients that were typically negative, underscore the
difficulties that arise when interpreting genotypic correlations as estimations of the probability that alleles are identical by descent.
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