Invasion Biology

Mechanisms of interference between invasive knotweeds and their native competitors

Madalin Parepa, Oliver Bossdorf
A series of experiments to understand allelopathic effects of invasive knotweeds (Fallopia ssp.) on native plants. We specifically test for the role that soil biota play in these interactions, and whether knotweed hybridisation increased allelopathic potential. In addition, we test whether invasive knotweeds have a greater ability to take advantage of heterogeneous resources than native plants.
(funded by SNF; in collaboration with Urs Schaffner (CABI Delémont), Ansgar Kahmen & Nina Buchmann (ETH Zurich)

Testing the generality of the novel weapons hypothesis of plant invasiveness

Corina del Fabbro, Daniel Prati
The novel weapon hypothesis states that introduced plants become invasive because they possess novel chemical compounds to which species in the invaded range are not adapted. We test this hypothesis in a comparative approach with a large set of invasive and native plants in Central Europe, both in greenhouse and field experiments. In particular we test that invasive plants have a more negative effect on other plant species than native plants and that soils from sites with a high contamination of invasive species have a more negative effect on plant performance than sites with a low contamination.
(funded by SNF)

Invasibility of Swiss grasslands

Juliane Preukschas, Michaela Zeiter, Markus Fischer, Andreas Stampfli*
Grasslands are among the most valued and biologically diverse ecosystems in Switzerland. They are increasingly under pressure from climate change and the invasion of exotic species. To better understand the effects of these different drivers of global change, and in particular their interactions, we carry out a large, multi-factorial seed addition experiment in which we test for the effects of summer drought, habitat productivity, origin of the sown species, and propagule pressure on invasibility of Swiss grasslands.
(funded by SNF; * Swiss College of Agriculture, Bern)

The global garlic mustard field survey

Oliver Bossdorf
A large-scale collaborative field study of the invasive plant garlic mustard (Alliaria petiolata) that asks whether plants in invasive North American populations are larger, less attacked by herbivores and more abundant than those in native European populations. A unique cross-continental project where many people (scientists, students, conservationists, naturalists) are involved. See for more infos.
(in collaboration with Rob Colautti (Duke University), Steve Franks (Fordham University) and the Global Invasions Network)

Pollinator visitation of native and alien plants

Christine Föhr-Heiniger, Markus Fischer
One potential key factor explaining plant invasiveness is the the degree to which exotic plants are able to attract native pollinators. To test this hypothesis, we take advantage of the large number of exotic and native plant species grown under similar climatic conditions in the Botanical Garden in Bern. We carry out repeated pollinator censusus on native and exotic species to test the hyptheses that (1) exotic plants generally attract fewer pollinators than native plants, but (2) invasive exotic plants attract more pollinators than non-invasive exotic plants.
(in collaboration with Mark van Kleunen, University of Konstanz, and Mialy Mialy Harindra Razanajatovo (University of Antananarivo)

Determinants and impacts of plant spread and invasion: a comparative and experimental approach

Wayne Dawson, Mark van Kleunen, Markus Fischer
We collect life-history data of species from the literature and use statistical meta-analysis to test whether species traits are associated with invasiveness of exotic species and rarity of native species. In addition, we do field and garden experiments with con-familial invasive alien species, non-invasive alien species, common native species, long-time rare species and recently declining species. These experiments assess species traits associated with invasiveness and rarity, invasibility and impact of invasion.
(funded by NCCR Plant Survival)

Experimental plant introduction: disentangling the roles of propagule pressure, soil disturbance and life-history traits

Anne Kempel, Thomas Chrobock, Markus Fischer, Mark van Kleunen
To quantify and disentangle the roles of species traits, soil disturbance and propagule pressure while controlling for time since introduction, we experimentally sowed seeds of 91 native and alien herbaceous species at different propagule pressures in 16 grassland sites with and without soil tilling. In separate greenhouse and common-garden experiments, we determine functional traits of the 91 species.
(funded by SNF)

The role of clonal life-history traits in plant invasions

Markus Fischer
By using experimental multi-species comparisons and meta-analysis of existing studies, we assess how clonal life-history traits, such as physiological intergration between ramets and foraging, contribute to invasiveness of clonal plant species.
(funded by Sino-Swiss Science and Technology Cooperation; in collaboration with Lidewij Keser & Mark van Kleunen (University of Konstanz), Yaobin Song, Fei-Hai Yu & Ming Dong (Chinese Academy of Sciences)