Green lizards were observed in the region in the image. Changes in the geography of the region caused the formation of a stream, which divided the region into two halves. The left half developed a dark green environment, and the right half a comparatively lighter green environment. As a result, two geographically isolated populations, dark and light green lizards inhabited either side of the stream. a stream running between two grassy regions

The region on the right has more light green lizards as a result of
. The new species will develop by way of
.