Figure 3.

Maize population dynamics and trait architecture. The genetic pool leading to modern maize has fluctuated greatly over its history, both in terms of absolute (census) population and effective population size, and also the selective pressures operating on it. Major divisions in maize history are indicated, with approximate durations noted. As many of the population values are unknown, the indicated population sizes are a range of likely estimates, with relative differences more important than absolute ones. Differences in the genetic architectures of certain traits may be due to the different lengths of time and population regimes that the traits have evolved under. (Note that although heterosis is not truly a trait, breeding for distinct heterotic groups can be seen as diversifying selection with heterosis as the final goal (Duvick, 2005)).