de Wit series experiments were conducted to determine the relative competitive ability and grain yields of four spring wheat varieties which include landrace Heshangtou and the modern varieties Longchun-8139, Dingxi-24 and Gaoyuan-602. Various pairs of varieties were grown in a mixed fashion and were compared with monoculture. The experiments were conducted in 2005 on the semiarid area of Loess Plateau, Gansu Province, China. Dingxi-24 had highest competitive ability, followed by Heshangtou, Longchun-8139 and Gaoyuan-602 in decreasing order, while yield ranged from the higher varieties of Dingxi-24, Longchun-8139, Gaoyuan-602 to lower landrace Heshangtou. The results showed that the varieties with higher competitive ability produced lower yield when the landrace Heshangtou were compared with the modern varieties Lonchun-8139 and Gaoyuan-602, but when a comparison was made among the modern varieties Dingxi-24, Longchun-8139 and Gaoyuan-602, the varieties with higher competitive ability had higher seed yield. The results showed that natural selection aiming at maximization of individual fitness by increase in competitive ability resulted in growth redundancy, with the more resources being invested into the competitive organs at the expense of the reproductive organs. The implications are that shifting resources into reproductive organs by reducing competitive ability through crop breeding can increase wheat production under certain environments, which is consistent with Donald’s ideotype. The reverse results revealed that if more resources were simultaneously invested into reproductive and competitive organs, the bred varieties can also perform better than varieties with lower competitive ability. Our results indicate that competitive ability is not necessarily correlated with seed yield and the key to increase yield is to develop varieties with higher harvest indices and total biomass. Natural selection aiming at maximization of individual fitness would inevitably result in occurrence of redundancy particularly in the case where more resources were partitioned into the competitive organs. Therefore, competitive ability is not the single criterion of crop breeding as Donald has proposed. Wheat breeding in semiarid areas should focus on the improvement of harvest index and increase of aboveground biomass.