SAN FRANCISCO, Calif., March 8, 2000 -- Chemistry has the periodic table of the elements, physics has the law of gravity, and biology has natural selection. According to new research published by San Francisco State University scientists in the March 9 issue of Nature, ecology may also one day get its own set of natural laws.
Applying a simple set of rules to a new food web model, the researchers revealed deep similarities between highly diverse ecosystems, suggesting the rules could be generalized.
"What makes this so compelling is that our model shows there are fundamental regularities in nature where ecologists thought there were none," said author Neo Martinez, an assistant biology professor who has made a career of studying food webs. "Having an accurate model of food webs gives ecologists a valuable tool for predicting the impact of biodiversity loss on ecosystems as different as oceans and deserts."
Working from their assertion that complex food webs arise from species having a simple pecking order of "who eats whom," Martinez and adjunct biology professor Richard Williams devised a theoretical model of food web organization based on two simple rules: one, that species higher up in the pecking order tend to eat lower-ordered species; and two, that if a species eats more than one species in the pecking order, it must also eat the species in between. While the basis of the pecking order is not yet known, similar rules are played out daily in nature: for example, a predator such as a wolf eats large and small herbivores such as deer and mice. Following the rules, it also eats intermediate herbivores, such as rabbits.
Called the "niche model," it is named for the theory's premise that each trophic species (a group of animal types that share the same predators and prey, such as some lizards) fits a specific niche based on what it eats and, in turn, what eats it.