Biogeographic comparisons of herbivore attack, growth and impact of Japanese knotweed between Japan and France

Abstract

Summary 1.To shed light on the process of how exotic species become invasive, it is necessary to study them both in their native and non-native ranges. Our intent was to measure differences in herbivory, plant growth and the impact on other species in Fallopia japonica in its native and non-native ranges. 2. We performed a cross-range full descriptive, field study in Japan (native range) and France (nonnative range). We assessed DNA ploidy levels, the presence of phytophagous enemies, the amount of leaf damage, several growth parameters and the co-occurrence of Fallopia japonica with other plant species of herbaceous communities. 3. Invasive Fallopia japonica plants were all octoploid, a ploidy level we did not encounter in the native range, where plants were all tetraploid. Octoploids in France harboured far less phytophagous enemies, suffered much lower levels of herbivory, grew larger and had a much stronger impact on plant communities than tetraploid conspecifics in the native range in Japan. 4. Our data confirm that Fallopia japonica performs better -plant vigour and dominance in the herbaceous community -in its non-native than its native range. Because we could not find octoploids in the native range, we cannot separate the effects of differences in ploidy from other biogeographic factors. To go further, common garden experiments would now be needed to disentangle the proper role of each factor, taking into account the ploidy levels of plants in their native and non-native ranges. 5. Synthesis. As the process by which invasive plants successfully invade ecosystems in their nonnative range is probably multifactorial in most cases, examining several components -plant growth, herbivory load, impact on recipient systems -of plant invasions through biogeographic comparisons is important. Our study contributes towards filling this gap in the research, and it is hoped that this method will spread in invasion ecology, making such an approach more common.

Can enemy release explain the invasion success of the diploid Leucanthemum vulgare in North America?

“…Reduced herbivore attack in the invaded compared to the native range has also been found by several other biogeographical studies (Wolfe 2002;Bossdorf et al 2005;Vilà et al 2005;Ebeling et al 2008;Adams et al 2009;Cripps et al 2010;Alba and Hufbauer 2012;Castells et al 2013;Maurel et al 2013;Blaisdell and Roy 2014;Cronin et al 2015). One reason for the low herbivore attack in the invaded range might be that there are no congeneric species native to North America (USDA, NRCS 2015), which decreases the probability for native specialist insect herbivores to extend their host range to include L. vulgare as a new host plant.…”

Comparison of defence and performance traits between one widespread clone and native populations in a major invasive plant species

“…We hypothesized that increased vigour of F. japonica observed in France (Maurel et al., ) was independent of genetically based changes. Our common garden experiment allowed us to compare French and Japanese populations in similar growing conditions; thus, the patterns that we observed are not due to plastic responses to environmental variability.…”

“…In a recent biogeographic comparison, Maurel et al. () confirmed that F. japonica from France performed better (longer and more ramified stems) than F. japonica from the native range. Maurel et al.…”

“…() suggested that the increased vigour in France could be seen as a plastic response to an environment with fewer enemies. However, measuring the stem length of F. japonica plants in their natural environments (Maurel et al., ) did not allow distinguishing between direct environmental effects (response to changing conditions) and evolutionary effects mediated, for example by different levels of polyploidy (Schlaepfer, Edwards, & Billeter, ; see te Beest et al., ). Indeed, testing for genetically based changes in phenotype between native and invasive conspecifics requires growing plants from both ranges in common gardens (Hierro, Maron, & Callaway, ).…”

From plant traits to invasion success: Impacts of the alienFallopia japonica(Houtt.) Ronse Decraene on two native grassland species

“…Furthermore, the evolution of increased competitive ability hypothesis (Blossey & Notzold 1995) postulates that because of the absence of specialized herbivores and pathogens in the new range, invasive plants shift their resource allocation from herbivore defence to increased growth or reproduction. In a biogeographic comparison of F. japonica populations in Europe and Japan, Maurel et al (2013) found "quasi-absence of herbivores, low leaf damage and increased plant vigour and growth" in the non-native range and explained that this was the reason why invasive F. japonica had competitive advantage over the native coexisting species. Several studies report that competition for light (i.e.…”