The fact that evolution can be rapid not only allows scientists to observe it in action, it also means that they can perform real-time experiments in the field to test their hypotheses by changing specific environmental parameters.
Recently, a team of scientists in Florida demonstrated that rapid evolution of a species can be triggered by a negative interaction with a competitor. To do so, the scientists introduced an invasive species of anole lizard to a group of small islands that shared the same lifestyle and diet as the native one, Anolis carolinensis.
The invader anoles forced the native ones to move from their original habitat on the forest floor and into the trees. Scientists were not only able to follow the rapid shift in the lifestyle of the native anole species (they perch higher and higher in the trees over time), but also observed that it involved rapid changes to their body shape. Within only 15 years (20 generations), the native anole species evolved larger toe pads with stickier scales, enabling them to climb more efficiently in their new, higher habitat.