Identifying mechanisms that structure ecological communities by snapping model parameters to empirically observed tradeoffs

Adam Thomas Clark, Clarence Lehman, David Tilman

Research output: Contribution to journalLetterpeer-review

20 Scopus citations


Theory predicts that interspecific tradeoffs are primary determinants of coexistence and community composition. Using information from empirically observed tradeoffs to augment the parametrisation of mechanism-based models should therefore improve model predictions, provided that tradeoffs and mechanisms are chosen correctly. We developed and tested such a model for 35 grassland plant species using monoculture measurements of three species characteristics related to nitrogen uptake and retention, which previous experiments indicate as important at our site. Matching classical theoretical expectations, these characteristics defined a distinct tradeoff surface, and models parameterised with these characteristics closely matched observations from experimental multi-species mixtures. Importantly, predictions improved significantly when we incorporated information from tradeoffs by ‘snapping’ characteristics to the nearest location on the tradeoff surface, suggesting that the tradeoffs and mechanisms we identify are important determinants of local community structure. This ‘snapping’ method could therefore constitute a broadly applicable test for identifying influential tradeoffs and mechanisms.

Original languageEnglish (US)
Pages (from-to)494-505
Number of pages12
JournalEcology letters
Issue number4
StatePublished - Apr 2018

Bibliographical note

Funding Information:
This work was supported by grants from the US National Science Foundation Long-Term Ecological Research Program, including DEB-8114302, DEB-8811884, DEB-9411972, DEB-0080382, DEB-0620652, and DEB-1234162, by the Cedar Creek Ecosystem Science Reserve, and by the University of Minnesota. A.T.C. was supported by an NSF GRFP, base award number 00006595, and by the Balzan Prize Foundation (awarded to D.T.). Computational resources were provided by the University of Minnesota Supercomputing Institute. Open access fees were paid by sDiv. We thank E. Borer, M. Burgess, M. Clark, J. Cowles, N. Eisenhauer, C. Farrior, G. Furey, B. Haegeman, F. Isbell, K. Kimmel, M. Loreau, C. Neuhauser, M. Thakur, S. Weisberg, and P. Wragg for advice and feedback on previous drafts of this manuscript. Lastly, we are very grateful to our editor, Margaret Mayfield, and to several anonymous reviewers, in particular for suggestions that helped us: (1) simplify our introduction to make it more understandable; (2) expand the interpretation of our mechanism-based model to encompass a wider range of systems; (3) better explain why snapping characteristics to the tradeoff surface should lead to improved predictions; and (4) frame our discussions of coexistence in terms of Chesson’s pairwise framework, which we hope make our results more broadly understandable.

Publisher Copyright:
© 2018 The Authors. Ecology Letters published by CNRS and John Wiley & Sons Ltd


  • Cedar Creek
  • LTER
  • coexistence mechanism
  • ecological community
  • grassland ecology
  • mechanistic model
  • predictive model
  • resource competition
  • tradeoff


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