Theoretical Ecology

, Volume 5, Issue 1, pp 141–151 | Cite as

Body size and species coexistence in consumer–resource interactions: A comparison of two alternative theoretical frameworks

  • Sumanta BagchiEmail author
  • Mark E. Ritchie
Original paper


Species coexistence involving trophic interactions has been investigated under two theoretical frameworks—partitioning shared resources and accessing exclusive resources. The influence of body size on coexistence is well studied under the exclusive resources framework, but has received less attention under the shared-resources framework. We investigate body-size-dependent allometric extensions of a classical MacArthur-type model where two consumers compete for two shared resources. The equilibrium coexistence criteria are compared against the general predictions of the alternative framework over exclusive resources. From the asymmetry in body size allometry of resource encounter versus demand our model shows, counterintuitively, and contrary to the exclusive resource framework, that a smaller consumer should be competitively superior across a wide range of supplies of the two resource types. Experimental studies are reviewed to resolve this difference among the two frameworks that arise from their respective assumptions over resource distribution. Another prediction is that the smaller consumer may have relatively stronger control over equilibrium resource abundance, and the loss of smaller consumers from a community may induce relatively stronger trophic cascades. Finally, from satiating consumers’ functional response, our model predicts that greater difference among resource sizes can allow a broader range of consumer body sizes to coexist, and this is consistent with the predictions of the alternative framework over exclusive resources. Overall, this analysis provides an objective comparison of the two alternative approaches to understand species coexistence that have heretofore developed in relative isolation. It advances classical consumer–resource theory to show how body size can be an important factor in resource competition and coexistence.


Coevolution Coexistence Foraging Predator prey Plant herbivore Resource partitioning Niche 



Support was received from National Science Foundation (DDIG DEB-0608287 to SB and DEB-0543398 to MER) and the National Center for Ecological Analysis and Synthesis (to MER) while preparing this manuscript. Additional support was received from Wildlife Conservation Society and Rufford Maurice Laing Foundation (to SB). We benefited from discussions with Charudutt Mishra, Oswald J. Schmitz, and William T. Starmer. We also thank the reviewers and the editors.

Supplementary material

12080_2010_105_MOESM1_ESM.doc (66 kb)
ESM 1 (DOC 65 kb)


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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.Department of BiologySyracuse UniversitySyracuseUSA
  2. 2.Nature Conservation FoundationMysoreIndia
  3. 3.Deparment of Ecosystem Science and ManagementTexas A&M UniversityCollege StationUSA

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