Fig. 3. Direct responses of particle size reduction index (PSRI) concentration to divergent selection for PSRI in four smooth bromegrass populations. Means are over four replicates, three locations, 3 yr, and two harvests. Solid lines represent linear selection responses (b) and dashed lines represent effects of drift (d). R² = 0.91, 0.97, 0.99, and 0.99 for Alpha, WB19e, Lincoln, and WB88S, respectively.