In ecosystems, organisms are constantly adjusting to geologic or climatic changes, but more importantly, to each other. If rabbits have long legs, then those coyotes in the population which are a little faster will provide more food to their offspring and thus tend to leave more genes in the population than the slow ones. The same holds for the rabbits. Bats and moths have been at this game for a long time. Some bats now vary the frequency when they detect a moth.
Species evolve in a particular geographical area, then gradually extend their range.
There are suitable environments in other parts of the world where they could tolerate the physical environment. Getting there takes time and luck. When they arrive they will change selective pressures for those species already there. Islands are good places for study since their remoteness permits few species to colonize them so their ecosystems remain rather simple. As long as no predators colonized the island, the only evolutionary pressures were to avoid overpopulation and avoid being blown out to sea.