Food Webs in Space: An Island Biogeographic Perspective

All ecologists are familiar with graphical portrayals of food webs such as that shown in Figure 29.1a—tinkertoy constructions of nodes (e.g., species) connected by lines (feeding relations). This depiction of food webs (or, more formally, its matrix equivalent) has without question helped articulate many important questions in community ecology (e.g., Pimm (1982), Pimm et al. (1991), and Cohen et al (1990)). Yet, as with any powerful conceptual schemata in science, this characterization of community organization both liberates—organizing one’s thoughts in fruitful directions—and enslaves—subtly constraining the questions one tends to ask. In particular, most descriptions of, and models about, food web structure make no explicit reference to space. But all ecological interactions, including trophic relations, are necessarily played out in a spatial arena. For some purposes this observation may well be irrelevant. However, it is becoming increasingly clear that the resolution of many classical problems in community ecology, from the coexistence of competitors (e.g., Hanski (1983)), to the stabilization of predator-prey interactions (e.g. Hassell et al. (1991), to the interpretation of species richness patterns (Cornell and Lawton, 1992), requires a consideration of spatial dynamics. Food web ecology, too, should profit from an explicit incorporation of spatial perspectives.