You are doing biology field work studying two species of lizards on a small volcanic island. Although quite hostile to each other when they accidentally meet, the two species usually remain in separate parts of the island. Species A seems to live and hunt insects only in the lower grassland part of the island. Species B seems to live and hunt only in the upper rocky areas. Species A has a short tongue but has longer legs and is a faster runner. Species B is short, squat, runs slower, but has a long tongue. You observe Species A chasing down some pretty large, fast- moving insects, while Species B meanders from rock to rock, using its long tongue to get insects hiding between rocks and in cracks. What principle of ecology do your two lizard species demonstrate?