I like the Garden of Eden senario. It puts a lot of food in 3 piles with a group of like colored swimmers on each pile.
So they are rewarded for staying in one spot initially. However, the food starts to disappear and then the rewards come for developing fast travel. However, there is no one to mate with at fast travel so only intermediate travel is really rewarded.
Before I went to a meeting, the yellows were borderling extinct and the blues were not far behind. I go to the meeting and when I return, the blues had a population explosion followed by the reds. So they are back even in population.
It is a pretty good game to demonstrate evolution.
Quath