Most plants compete for resources: competition has been shown to limit growth in both agricultural and naturally- occurring plants. Many studies have investigated the importance of competition (e.g. yield-density relationships, effects of weeds on crops). However, very little is known about the evolutionary importance of competition. To what degree has competition been important in the evolution of plant morphology, physiology, and phenology? There are four evolutionary alternatives or outcomes for competing plants: resource partitioning, increased uptake of resources, increased efficiency of resource use, and interference mechanisms. The investigator has predicted which alternative is most likely to occur in different types of competitive environments. The proposed research directly follows the evolution of plants in different competitive environments. Brassica rapa L. will be grown at high densities for ten discrete generations. Environments will differ in the presence and absence of interspecific competitors and fertilizer. Each generation, the largest 20% of the individuals will be selected to be pollinated and to provide seed for the next generation. The investigator will monitor competitive characteristics of individuals of each generation for changes in plant performance and traits. The results will demonstrate which of the four evolutionary alternatives are most likely to occur in different conditions.
