R* rule (ecology)

The R* rule (also called the resource-ratio hypothesis) is a hypothesis in community ecology that attempts to predict which species will become dominant as the result of competition for resources.[1] The hypothesis was formulated by American ecologist David Tilman.[2] It predicts that if multiple species are competing for a single limiting resource, then whichever species can survive at the lowest equilibrium resource level (i.e., the R*) can outcompete all other species.[1] If two species are competing for two resources, then coexistence is only possible if each species has a lower R* on one of the resources.[1] For example, two phytoplankton species may be able to coexist if one is more limited by nitrogen, and the other is more limited by phosphorus.

A large number of experimental studies have attempted to verify the predictions of the R* rule. Many studies have shown that when multiple plankton are grown together, the species with the lowest R* will dominate, or coexist if they are limited by multiple resources.[3] There are fewer tests of the R* rule in communities of larger organisms, in part because of the difficulty of creating a situation in which only a single resource is limiting.[3][4] However, some studies have used the R* rule with multiple resources to predict which groups of plants will be able to coexist.[5]

  1. ^ a b c Tilman, David (1982). Resource competition and community structure. Monographs in Population Biology. Vol. 17. Princeton: Princeton University Press. pp. 1–296. ISBN 9780691083025. PMID 7162524.
  2. ^ Wilson, J. Bastow; Spijkerman, Elly; Huisman, Jef (May 2007). "Is There Really Insufficient Support for Tilman's * Concept? A Comment on Miller et al". The American Naturalist. 169 (5): 700–706. doi:10.1086/513113. PMID 17427140. S2CID 30798966.
  3. ^ a b Cite error: The named reference grover1997 was invoked but never defined (see the help page).
  4. ^ Miller, Thomas E.; Burns, Jean H.; Munguia, Pablo; Walters, Eric L.; Kneitel, Jamie M.; Richards, Paul M.; Mouquet, Nicolas; Buckley, Hannah L. (April 2005). "A Critical Review of Twenty Years' Use of the Resource-Ratio Theory". The American Naturalist. 165 (4): 439–448. doi:10.1086/428681. PMID 15791536. S2CID 30750778.
  5. ^ Dybzinski, Ray; Tilman, David (September 2007). "Resource Use Patterns Predict Long-Term Outcomes of Plant Competition for Nutrients and Light". The American Naturalist. 170 (3): 305–318. doi:10.1086/519857. PMID 17879183. S2CID 10048315.