Competition between <Emphasis Type="Italic">Lythrum salicaria</Emphasis> and a rare species: combining evidence from experiments and long-term monitoring |
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Authors: | Madlen Denoth Judith H Myers |
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Institution: | (1) Department of Zoology, The University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada, V6T 1Z4;(2) Present address: Département de biologie, Unité d’écologie et évolution, Université de Fribourg, Chemin du Musée 10, 1700 Fribourg, Switzerland |
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Abstract: | The rare endemic plant Sidalcea hendersonii (Henderson’s checker-mallow) occurs in tidal marshes of the Pacific Northwest and may be threatened by Lythrum salicaria (purple loosestrife), a European invader plant. We compared the abundances of Lythrum and Sidalcea in a wetland in British Columbia (Canada) in 1999 to those measured in 1979 to track changes in both species. Although the
frequency of Sidalcea decreased by more than 50%, and that of Lythrum increased by almost 20%, there was no significant relationship between the changes of the two species. We assessed the potential
effects of competition by Lythrum on Sidalcea in field and patio experiments. In the field, we measured the response of Sidalcea to the removal of Lythrum over a two-year period and compared this to the response of Sidalcea to the removal of native species and in unmanipulated control plots. Removal of Lythrum significantly improved the vegetative performance of Sidalcea compared to the removal of randomly selected native plants and the control treatment in the first year. In the second year,
the performance of Sidealcea did not differ significantly with treatment. Removals did not influence the reproductive performance of Sidalcea in either year. A one-year additive experiment, carried out in pots, compared the competitive effect of Lythrum on Sidalcea with that of two native species. Lythrum’s impact on Sidalcea was not consistently stronger than that of the native species. Collectively, these results do not indicate a strong impact
of Lythrum on the reproduction or abundance of Sidalcea. |
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Keywords: | Invasive plant Purple loosestrife Removal experiment Sidalcea hendersonii Tidal wetland |
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