size limit. Using expression (5.7) for Axil), the average change due to selection in the leading order can be written as (aarl)s = 61V-1 (Xkl(AX)k XTAXD = 6N-1 (Eaki(skxj) — E aij(xkxixj)), (5.9) where (.) denotes the average in the neutral stationary state (6 = 0). So far we have only considered