Anolis sagrei, the Cuban brown anole, was introduced to Florida and spread rapidly. Where the two species meet, green anoles tend to occupy higher and thinner perches, a shift that can be seen within a single season and looks at first like simple behavioural avoidance.
Yoel Stuart and colleagues, publishing in Science in 2014, tested whether the shift had produced heritable change. Working on small islands in a Florida lake, some invaded by brown anoles and some not, they measured toe pads on green anoles before and after invasion. On invaded islands the pads became larger with more lamellae, the adhesive scales that let an anole hold a smooth or narrow surface. The change appeared over roughly fifteen years and was consistent across replicate islands.
The result is often described as evolution in twenty generations, which is accurate, but two cautions belong with it. The magnitude is modest, a few percent, not a transformation. And character displacement of this kind requires the replicate-island design to be convincing, since a single island could reflect drift.