Figure 2

Regression of the phenotypic value of tarsus on the breeding value (here BVincl) of tarsus. The breeding value is expressed in mm by adding the population mean tarsus length to the BV of each individual. Thus, the x-axis illustrates the estimated genetically determined tarsus length that would be achieved under a standard environmental condition, while the y-axis illustrates the actual phenotypic tarsus length that was realised under the actual environmental conditions of the individual. The residuals from the regression represent the environmental contribution (RESincl) to tarsus for each individual. Note that estimates of BV are biased towards the phenotype because the phenotype of an individual contributes to the estimation of its BV (BVincl). Hence, the correlation is stronger (r² = 0.83) than expected from the heritability (h² = 0.55). The slope of the regression is 1.59.