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PNAS: Chris T. Darimont et al., Human predators outpace other agents of trait change in the wild

Human predators outpace other agents of trait change in the wild

  1. Chris T. Darimonta,b,1,
  2. Stephanie M. Carlsonc,
  3. Michael T. Kinnisond,
  4. Paul C. Paquete,
  5. Thomas E. Reimchena and
  6. Christopher C. Wilmersb

+Author Affiliations

  1. aDepartment of Biology, University of Victoria, P.O. Box 3020, Stn CSC, Victoria, BC, Canada V8W 3N5;
  2. bDepartment of Environmental Studies, University of California, 405 Interdisciplinary Sciences Building, 1156 High Street, Santa Cruz, CA 95060;
  3. cDepartment of Environmental Science, Policy, and Management, University of California, 137 Mulford Hall #3114, Berkeley, CA 94720;
  4. dSchool of Biology and Ecology, University of Maine, 321 Murray Hall, Orono, ME 04469; and
  5. eDepartment of Environmental Design, University of Calgary, 2500 University Drive Northwest, AB, Canada T2N 1N4

  1. Edited by Gretchen C. Daily, Stanford University, Stanford, CA, and approved November 21, 2008 (received for review September 15, 2008)

Abstract

The observable traits of wild populations are continually shaped and reshaped by the environment and numerous agents of natural selection, including predators. In stark contrast with most predators, humans now typically exploit high proportions of prey populations and target large, reproductive-aged adults. Consequently, organisms subject to consistent and strong ‘harvest selection’ by fishers, hunters, and plant harvesters may be expected to show particularly rapid and dramatic changes in phenotype. However, a comparison of the rate at which phenotypic changes in exploited taxa occurs relative to other systems has never been undertaken. Here, we show that average phenotypic changes in 40 human-harvested systems are much more rapid than changes reported in studies examining not only natural (n = 20 systems) but also other human-driven (n = 25 systems) perturbations in the wild, outpacing them by >300% and 50%, respectively. Accordingly, harvested organisms show some of the most abrupt trait changes ever observed in wild populations, providing a new appreciation for how fast phenotypes are capable of changing. These changes, which include average declines of almost 20% in size-related traits and shifts in life history traits of nearly 25%, are most rapid in commercially exploited systems and, thus, have profound conservation and economic implications. Specifically, the widespread potential for transitively rapid and large effects on size- or life history-mediated ecological dynamics might imperil populations, industries, and ecosystems.

Footnotes

  • 1To whom correspondence should be addressed. E-mail: darimont@ucsc.edu

  • Author contributions: C.T.D., M.T.K., P.C.P., and T.E.R. designed research; C.T.D., S.M.C., and C.C.W. performed research; C.T.D., S.M.C., and C.C.W. analyzed data; and C.T.D., S.M.C., M.T.K., P.C.P., T.E.R., and C.C.W. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

Link to abstract: http://www.pnas.org/content/early/2009/01/12/0809235106.abstract