Endophyten und invasive Pflanzen: Why beeinflussen endophytische Pilze Wachstum, Umwelttoleranz und Konkurrenzstärke von invasiven Knöterichen?
Zusammenfassung der Projektergebnisse
There is increasing evidence that microbes play a key role in some plant invasions, but much of this evidence is rather coarse, and we often do not know which specific microorganisms promote plant invasiveness. A diverse and widespread but little understood group of plant-associated microbes are the fungal root endophytes of the order Sebacinales. They had previously been found associated with exotic populations of invasive knotweed (Reynoutria ssp.) in Europe, but their effects on the invaders were so far unknown, mainly because Sebacinales are usually difficult to isolate and cultivate, and therefore experimental tests of their ecological effects have been rare. We took advantage of the recent isolation of a common Sebacinales strain, Serendipita herbamans, in our group, to conduct to series of controlled experiments that tested the effects of S. herbamans inoculation on knotweed growth, as well as on knotweed invasiveness in native plant communities. We combined these experiments with an extensive field survey of root endophytic fungi in invasive knotweed populations. We confirmed through immunofluorescence microscopy and qPCR that after inoculation S. herbamans can indeed quickly colonize invasive knotweed, but that this colonization is highly environment-dependent, and it mainly occurs under some environmental stress conditions. Similarly, the effect of S. herbamans on the growth of knotweed can be positive, negative or neutral, depending on environmental conditions. Particularly under low-nutrient conditions, S. herbamans appeared to have beneficial effects on knotweed, whereas under shade conditions the interaction became antagonistic, with detrimental effects on knotweed growth. In another experiment, we showed that inoculation with S. herbamans also affected its palatability to a generalist herbivore (snails), probably through influencing secondary compounds and/or leaf nutrient contents. Having established diverse effects on invasive knotweed, we tested endophyte effects on native plants, in particular known competitors of knotweed in invasive populations. In a series of experiments we found that S. herbamans can colonize a variety of native plant species, and that it can influence their germination and growth in different ways, mostly negative. When tested individually, knotweed appeared to benefit most from S. herbamans inoculation, compared to a range of native plants. Because of this we then hypothesized that inoculation with S. herbamans should shift community composition in favour of invasive knotweed, when the plants were all growing together. To test this, we conducted an additional mesocosm experiment with communities of native plants plus knotweed. However, in this final experiment, we did not find any significant effects of S. herbamans on plant growth or knotweed invasiveness, indicating that plant-fungi and plant-plant interactions may influence each other, and more generally the difficulty of understanding ecological communities from individual species interactions. In the last work package, we surveyed more broadly the diversity of fungi associated belowground with knotweed in invasive populations, using next-generation sequencing, and we confirmed the presence of Sebacinales in most of them. However, there was a much larger fungal diversity, with Sebacinales being only a minor component, which suggests that while Sebacinales may play some role in invasive populations – and our controlled experiments provide only mixed support for this – there are many other other knotweed-microbe interactions that could be subjects of future research.
Projektbezogene Publikationen (Auswahl)
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(2017) A common endophyte affects the growth and herbivore resistance of invasive knotweed. 3rd International Congress on Biological Invasions, Hangzhou, China, 19-23 November 2017
Bossdorf O, Garnica S, Hamard S, Liao Z, Parepa M, Waller F
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(2017) Does invasive knotweed (Fallopia japonica and Fallopia x bohemica) benefit from interactions with the novel endophytic fungus Serendipita herbamans? Annual Meeting of the Plant Population Biology section of the German Ecological Society, Halle, 18-20 May 2017
Hamard S, Liao Z, Garnica S, Parepa M, Bossdorf O
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(2018) A common endophyte affects the growth and herbivore resistance of invasive knotweed. Annual Meeting of the Plant Population Biology section of the German Ecological Society, Innsbruck, 3-5 May 2018
Bossdorf O, Garnica S, Hamard S, Liao Z, Parepa M, Waller F
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(2018) Invasion of Asian knotweed into European plant communities: fluctuating resources, biotic interactions, and a very large clone. 3rd International Conference on Biological Invasion and Global Change, Kaifeng, China, 4-8 November 2018
Bossdorf O, Fischer M, Garnica S, Liao Z, Kahmen A, Schaffner U, Waller F, Zhang Y, Parepa M
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(2019) The endophytic fungus Serendipita herbamans affects the germination of many herbaceous plants and colonizes them early. Annual Meeting of the Plant Population Biology section of the German Ecological Society, Warsaw, 23-25 May 2019
Bossdorf O, Breit M, Lang E, Waller F, Parepa M
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(2022) Environmental stress determines the colonization and impact of an endophytic fungus on invasive knotweed. Biological Invasions
Garnica S, Liao Z, Hamard S, Waller F, Parepa M, Bossdorf O
