We considered a base model in which variance is partitioned into a polygenic component σg 2 and an environmental component σe 2. As usual, the environmental component is unique to each individual, whereas the polygenic component is shared between individuals in proportion to their kinship coefficient. Thus, if Yi is the observed trait measurement for individual i, we define its variance as Var(Yi) = σg 2 + σe 2 and the covariance between measurements for a pair of individuals i and j with kinship ϕij as Cov(Yi, Yj) = 2 ϕij σg 2.
