Journal Article

Response to enemies in the invasive plant <i>Lythrum salicaria</i> is genetically determined

Srijana Joshi and Katja Tielbörger

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 110, issue 7, pages 1403-1410
Published in print November 2012 | ISSN: 0305-7364
Published online April 2012 | e-ISSN: 1095-8290 | DOI:
Response to enemies in the invasive plant Lythrum salicaria is genetically determined

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry


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Background and Aims

The enemy release hypothesis assumes that invasive plants lose their co-evolved natural enemies during introduction into the new range. This study tested, as proposed by the evolution of increased competitive ability (EICA) hypothesis, whether escape from enemies results in a decrease in defence ability in plants from the invaded range. Two straightforward aspects of the EICA are examined: (1) if invasives have lost their enemies and their defence, they should be more negatively affected by their full natural pre-invasion herbivore spectrum than their native conspecifics; and (2) the genetic basis of evolutionary change in response to enemy release in the invasive range has not been taken sufficiently into account.


Lythrum salicaria (purple loosestrife) from several populations in its native (Europe) and invasive range (North America) was exposed to all above-ground herbivores in replicated natural populations in the native range. The experiment was performed both with plants raised from field-collected seeds as well as with offspring of these where maternal effects were removed.

Key Results

Absolute and relative leaf damage was higher for introduced than for native plants. Despite having smaller height growth rate, invasive plants attained a much larger final size than natives irrespective of damage, indicating large tolerance rather than effective defence. Origin effects on response to herbivory and growth were stronger in second-generation plants, suggesting that invasive potential through enemy release has a genetic basis.


The findings support two predictions of the EICA hypothesis – a genetically determined difference between native and invasive plants in plant vigour and response to enemies – and point to the importance of experiments that control for maternal effects and include the entire spectrum of native range enemies.

Keywords: Biological control; field experiment; herbivory; purple loosestrife; enemy release; EICA hypothesis; invasion; Lythrum salicaria

Journal Article.  5400 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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