 An example of ant-plant mutualism: ants visit nectar-secreting glands on a barrel cactus. Photo: M. Lanan |
In Chapter 6 of The Origin of Species, Charles Darwin wrote: “If it could be proved that any part of the structure of any one species had been formed for the exclusive good of another species, it would annihilate my theory, for such could not have been produced through natural selection.” Thus, Darwin recognized that mutualism – the reciprocal exchange of benefits between members of two species – poses a critical puzzle for biologists. Mutualism is not a minor curiosity, either: it is in fact ubiquitous in the natural world. For example, over 80% of plants are associated with mycorrhizal fungi; in tropical rainforests, the vast majority of plants depend on animals for pollination and seed dispersal.
Mutualism has been argued to lie at the root of phenomena as diverse as the origin of the eukaryotic cell, the invasion of new adaptive zones, and the pattern of elevated species diversity in tropical forests. However, while the ecological importance of mutualism is frequently asserted and the evolutionary puzzle it poses frequently pointed out, most of the most basic questions about its ecology and evolution have yet to be addressed. Perhaps symbolic of this point, only about 12% of pages that modern ecology texts devote to pairwise interactions deal with mutualism; the large majority of these pages simply recount interesting natural history stories. In essence, mutualisms have been treated by biologists as a grab-bag of phenomena bearing little relation to each other.
The long-term goal of my research programme is to develop a synthetic view of mutualism that cuts across boundaries of particular forms of benefit and that identifies common ecological patterns and processes. Currently, two broad questions drive my research. First, what are the costs and benefits of mutualism; how do they drive the ecology and evolution of the interacting species, particularly given the apparent advantage of cheating? Second, how do mutualisms function and evolve in community settings? I pursue these questions via conceptual and theoretical studies aimed at identifying empirical generalities and via empirical studies on some particularly interesting systems. |
