Original Paper

Biological Invasions

, Volume 9, Issue 6, pp 715-722

Rapid shifts in the chemical composition of aspen forests: an introduced herbivore as an agent of natural selection

  • Joseph K. BaileyAffiliated withDepartment of Ecology and Evolutionary Biology, University of TennesseeDepartment of Biological Sciences, Northern Arizona UniversityMerriam-Powell Center for Environmental Research, Northern Arizona University Email author 
  • , Jennifer A. SchweitzerAffiliated withDepartment of Ecology and Evolutionary Biology, University of TennesseeSchool of Forestry, Northern Arizona UniversityMerriam-Powell Center for Environmental Research, Northern Arizona University
  • , Brian J. RehillAffiliated withDepartment of Chemistry, United States Naval Academy
  • , Duncan J. IrschickAffiliated withDepartment of Biology, University of Massachusetts
  • , Thomas G. WhithamAffiliated withDepartment of Biological Sciences, Northern Arizona UniversityMerriam-Powell Center for Environmental Research, Northern Arizona University
  • , Richard L. LindrothAffiliated withDepartment of Entomology, University of Wisconsin

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Abstract

The global ecological impacts of introduced and exotic species can be dramatic, leading to losses in biodiversity and ecosystem “meltdown”, however, the evolutionary impacts of introduced species are much less understood. Further, very few studies have examined whether mammalian herbivores can act as agents of natural selection for plant traits. We examined the hypothesis that variation in aspen phytochemistry resulted in selective herbivory by Cervus elaphus (elk), an introduced mammalian herbivore. With the experimental removal of a large elk exclosure, elk selectively eliminated 60% of an aspen population previously protected from herbivory resulting in a dramatic shift in the phytochemical composition of the aspen forest. Selection gradients (β) varied from 0.52 to 0.66, well above average relative to other studies of selection. These results indicate that introduced herbivores can have rapid evolutionary consequences even on long lived native species. Because there are fundamental links between phytochemistry, biodiversity and ecosystem processes, the effects of an introduced herbivore are likely to have cascading impacts on the services ecosystems provide.

Keywords

Aspen Elk Herbivory Introduced species Natural selection Phytochemistry Populus Plant animal interactions