The mutual dependence of pollinators and flowering plants is one of the most common kinds of beneficial interactions. Often, each is vital for the survival of the other. For example, on Table Mountain, in South Africa, a large proportion of all red flowers are pollinated by a single species of butterfly. That butterfly is declining in numbers. If it goes extinct, all of the flowers may go extinct with it, unless a new pollinator arrives that is able fill its niche.
Sometimes, the relationship between a pollinator and a flower is exclusive, each depending just on the other. Sometimes, it is much more general, where one or both interacts with several other species. Species of hummingbirds show this whole range of preferences. But flowers that are pollinated exclusively by hummingbirds have usually evolved to be deep, so that only a birdΓÇÖs beak can reach down far enough to gain the nectar reward.
