Abstract:
One common class of ant-plant mutualism involves ants that defend plants from natural enemies in return for food and sometimes shelter. Studies of these interactions have played a major role in shaping our broad understanding of mutualism. Their central contribution has come via their development of approaches to measuring the benefits, costs, and net outcomes of mutualism, and their explicit consideration of variability in all of these phenomena. Current research on these interactions is suggesting ecological and evolutionary hypotheses that may be applicable to many other forms of mutualism. It is also generating comparative data for testing the few general theories about mutualism that currently exist.
Abstract:
Examines the role of style lengths in the interaction between the common monoecious Ficus pertusa species and its pollinator Pegoscapus silvestrii (Agaonidae). The author first predicts seed and wasp production from measurements of fig styles and wasp ovipositors, then compares predicted and actual numbers produced. Several other, as yet untested, factors that may limit pollinator fecundity as suggested. The study was conducted in Monteverde, Puntarenas Province, Costa Rica. -from Author
Abstract:
In generalized, multispecies mutualisms, competition among members of one guild can influence the net benefits that each species in the other guild receives. Hence seasonal factors that affect the dynamics of competition can also affect net benefits, especially if the benefit or cost of mutualism also varies seasonally. In the Sonoran Desert, two common species of generalist ants compete for access to extrafloral nectaries on the fishhook barrel cactus Ferocactus wislizeni, but their relative abundances vary seasonally; one ant dominates more cacti in winter/spring, and the other in summer/autumn. Recently, a third ant species, which also varies in abundance seasonally, has appeared at our study sites and is competing with resident ants for access to cactus nectaries. This empirical system motivated us to examine a metapopulation model of competition for patches in an open system with periodic forcing. We use the model to: (1) illustrate three ways in which competing species may differ in their sensitivities to environmental conditions that are consistent with seasonally displaced patterns of abundance; (2) ask under what conditions the invasion of a third competitor into a two-species system could alter the sensitivity of the system to environmental forcing at low vs. high frequency; and (3) show how differences among competitors in the pattern of seasonal forcing alone can dramatically alter the outcome of a competitor invasion. We discuss implications of these results for the ways in which seasonal variation among competing mutualists, and the benefits and costs of mutualism, may affect the functioning of generalized, facultative mutualisms. © 2005 by the Ecological Society of America.
