Letter

Nature 443, 989-992 (26 October 2006) | doi:10.1038/nature05202; Received 8 July 2006; Accepted 5 September 2006

Effects of biodiversity on the functioning of trophic groups and ecosystems

Bradley J. Cardinale1, Diane S. Srivastava2, J. Emmett Duffy3, Justin P. Wright4, Amy L. Downing5, Mahesh Sankaran6 & Claire Jouseau7

  1. Department of Ecology, Evolution and Marine Biology, University of California at Santa Barbara, Santa Barbara, California 93106, USA
  2. Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
  3. Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point, Virginia 23062, USA
  4. Department of Biology, Duke University, Durham, North Carolina 27708, USA
  5. Department of Zoology, Ohio Wesleyan University, Delaware, Ohio 43015, USA
  6. Institute of Integrative & Comparative Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
  7. Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, New York 10027, USA

Correspondence to: Bradley J. Cardinale1 Correspondence and requests for materials should be addressed to B.J.C. (Email: cardinale@lifesci.ucsb.edu).

Over the past decade, accelerating rates of species extinction have prompted an increasing number of studies to reduce species diversity experimentally and examine how this alters the efficiency by which communities capture resources and convert those into biomass1, 2. So far, the generality of patterns and processes observed in individual studies have been the subjects of considerable debate3, 4, 5, 6, 7. Here we present a formal meta-analysis of studies that have experimentally manipulated species diversity to examine how it affects the functioning of numerous trophic groups in multiple types of ecosystem. We show that the average effect of decreasing species richness is to decrease the abundance or biomass of the focal trophic group, leading to less complete depletion of resources used by that group. At the same time, analyses reveal that the standing stock of, and resource depletion by, the most species-rich polyculture tends to be no different from that of the single most productive species used in an experiment. Of the known mechanisms that might explain these trends, results are most consistent with what is called the |[lsquo]|sampling effect|[rsquo]|, which occurs when diverse communities are more likely to contain and become dominated by the most productive species. Whether this mechanism is widespread in natural communities is currently controversial. Patterns we report are remarkably consistent for four different trophic groups (producers, herbivores, detritivores and predators) and two major ecosystem types (aquatic and terrestrial). Collectively, our analyses suggest that the average species loss does indeed affect the functioning of a wide variety of organisms and ecosystems, but the magnitude of these effects is ultimately determined by the identity of species that are going extinct.

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