When Is It Mutualism?

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Abstract
Whence my possibly cryptic title? At the simplistic level that most of us first encounter plant-pollinator relations— in a basic textbook, an introductory lecture, or a television documentary—three elements tend to be stressed. First, there is a matchup between particular types of animals and particular types of flowers. Not only do animals visit plants nonrandomly within local communities, but also certain suites of floral characters seem to covary with each other and with patterns of animal visitation at regional scales and possibly global scales. These suites of covarying characters constitute "pollination syndromes" (Fægri and van der Pijl 1979). Of the relationship between plants and animals that has produced these matches, two aspects tend to be stressed: it is mutualistic, and it reflects coevolution between plant and animal. The mutualism seems com- paratively obvious: visitors usually get fed; visited plants donate and receive pollen. The coevolutionary aspect is necessary to explain striking adaptive matches such as the extraordinary correspondence between extravagantly long nectar spurs and extravagantly long insect tongues. In- cautious extrapolation from these three elements could lead one to think that each plant might be hooked to its own specific pollinator, that the identity of that pollinator could be inferred from the floral morphology, that the * This article was first presented as the presidential address delivered to the American Society of Naturalists at a joint meeting with the Society for the Study of Evolution and the Society of Systematic Biologists, 2001. It was written for oral presentation.