Bi-directional population LS means  ±  standard errors for carbon isotope composition (δ¹³C, A1) and height (h, B1) in the 2 trial sites (axis X: Xe, axis Y: Me). Symbols: Arenas (A), Oria (O) and Mimizan (M) the 1st year. Bold letters the 2nd year. Bi-directional LS means  ±  standard errors for δ¹³C (A2) and h (B2) in a subsample of families present in both progeny trial sites. Symbols: ●, 1st year;  ◯ , 2nd year. Diagonal lines represent equal values in both sites.