An experimental test of the evolution of increased competitive ability hypothesis in goldenrod, <Emphasis Type="Italic">Solidago gigantea</Emphasis> |
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Authors: | Email author" target="_blank">Gretchen?MeyerEmail author Robert?Clare Ewald?Weber |
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Institution: | (1) University of Wisconsin-Milwaukee Field Station, 3095 Blue Goose Road, Saukville, WI 53080, USA;(2) Geobotanical Institute, Federal Institute of Technology, Zürichbergstr. 38, 8044 Zurich, Switzerland |
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Abstract: | The mechanisms that allow introduced plants to become invasive are poorly understood. Here, we present a test of the evolution
of increased competitive ability hypothesis, which holds that because specialized natural enemies may be absent from the introduced
range, exotic plants may evolve to invest less in anti-herbivore defenses and thereby gain a competitive advantage over native
plants. We grew Solidago gigantea plants derived from both the native range (North America) and the invasive range (Europe) in a common garden in the native
range for 2 years. Half the plants were treated with insecticide to protect them from insect herbivores and the other half
were exposed to insects that colonized the garden from nearby fields. Insect herbivore biomass was significantly higher on
European plants than US plants in the first year but not the second. European plants were more heavily attacked by pathogens
in both years of the study. When exposed to insect herbivores, US plants produced more seed than European plants, but when
plants were protected from herbivores, seed production was equivalent between US plants and European plants. The presence
of insect herbivores suppressed seed production of European plants much more than that of US plants, even though the level
of herbivory experienced by European and US plants was similar in the second year, suggesting that the ability to tolerate
herbivory was diminished in European plants. These results partially support the EICA hypothesis: plants from the introduced
range were more susceptible to some natural enemies and benefited more from insect removal than plants from the native range.
The prediction that European plants would perform better than US plants in the absence of insect herbivores was not supported.
Electronic Supplementary Material Supplementary material is available for this article at |
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Keywords: | Enemy release Herbivory Introduced species Invasive species Solidago gigantea |
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