2-D Adaptive Landscape - Simulation
In the simulation to the right, a total of 3 adaptive peaks are present (initially located in the same place). Each peak can be adjusted with respect to its location on the trait axis (mean), its width (variance) as well as its height. The initial mean, variance, and size of the population can also be adjusted.
The population size can range from 20 to 200. If a large amount of genetic drift is desired, the population size should be set to 20. If a small amount of drift is desired, the population size should be set to 200. Note that the simulation will run slower if a large population is used.
If mutation is allowed, the population will be able to explore areas that selection alone cannot.
Pressing the run button allows the population to begin moving around on the adaptive landscape. While the population is adapting to the landscape, the peaks can be adjusted so that a changing environment can be simulated.
Each of the yellow dots represents an individual. Note that no individual actually moves on the adaptive landscape (changes in its trait value). Instead, the population as a whole moves as it adapts to the landscape. When an individual dies, it is erased and replaced by an individual that may have a different trait value. The trait value of a newly born individual is a function of its parents' trait values. The parents are chosen either randomly or, if desired, through mate choice (positive assortative mating).
Mate preference may, if the adaptive landscape is conducive, allow the population to diverge genetically. You will notice this divergence in two ways:1) the population will occupy two fitness peaks simultaneously, and 2) the trait and preference will become correlated. This divergence is only temporary, however, since the population size is always constant and some degree of genetic drift is always operating.
The value of the trait and preference for each individual is presented in the upper left area of the graph. When the trait and preference are correlated, you will notice that the two sets of short bars appear to become one set of long bars.