Consumer versus resource control of producer diversity depends on ecosystem type and producer community structure

Helmut Hillebrand, Daniel S. Gruner, Elizabeth T. Borer, Matthew E S Bracken, Elsa E. Cleland, James J. Elser, W. Stanley Harpole, Jacqueline T. Ngai, Eric W. Seabloom, Jonathan B. Shurin, Jennifer E. Smith

Research output: Contribution to journalArticlepeer-review

254 Scopus citations

Abstract

Consumer and resource control of diversity in plant communities have long been treated as alternative hypotheses. However, experimental and theoretical evidence suggests that herbivores and nutrient resources interactively regulate the number and relative abundance of coexisting plant species. Experiments have yielded divergent and often contradictory responses within and among ecosystems, and no effort has to date reconciled this empirical variation within a general framework. Using data from 274 experiments from marine, freshwater, and terrestrial ecosystems, we present a cross-system analysis of producer diversity responses to local manipulations of resource supply and/or herbivory. Effects of herbivory and fertilization on producer richness differed substantially between systems: (i) herbivores reduced species richness in freshwater but tended to increase richness in terrestrial systems; (ii) fertilization increased richness in freshwater systems but reduced richness on land. Fertilization consistently reduced evenness, whereas herbivores increased evenness only in marine and terrestrial ecosystems. Producer community evenness and ecosystem productivity mediated fertilization and herbivore effects on diversity across ecosystems. Herbivores increased producer richness in more productive habitats and in producer assemblages with low evenness. These same assemblages also showed the strongest reduction in richness with fertilization, whereas fertilization increased (and herbivory decreased) richness in producer assemblages with high evenness. Our study indicates that system productivity and producer evenness determine the direction and magnitude of top-down and bottom-up control of diversity and may reconcile divergent empirical results within and among ecosystems.

Original languageEnglish (US)
Pages (from-to)10904-10909
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume104
Issue number26
DOIs
StatePublished - Jun 26 2007

Bibliographical note

Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.

Keywords

  • Evenness
  • Fertilization
  • Herbivory
  • Metaanalysis
  • Species richness

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