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

Abstract

Aim The success of invasive species in their introduced range is often assumed to result from evolutionary changes in defence and growth traits, or as a response to more favourable conditions. The latter is assumed particularly for species exhibiting low, or even no, sexual reproduction in the introduced range. Location and Methods Here, we compared Japanese (native range) and French (introduced range) populations of Fallopia japonica under common growth conditions in a glasshouse. We measured height, aboveground and belowground mass, stem stiffness, leaf toughness and secondary metabolites found in hydroalcoholic extracts of rhizomes of F. japonica, as well as the competitive response of Rubus caesius (a co‐occurring native species in the invaded range) in the presence of F. japonica from both ranges. Results Aboveground biomass, height, stem stiffness and composition of secondary metabolites were not significantly different between the two ranges, showing that increased aboveground vigour observed in situ in France is probably the result of a plastic response following the release of abiotic or biotic constraints from the native range. On the other hand, belowground mass, effect on R. caesius, and leaf toughness were all higher in French populations, suggesting increases in competitive ability and defence mechanisms. These differences between France and Japan may be explained either by post‐introduction evolution or by the introduction in Europe, in nineteenth century, of an exceptionally vigorous clone (pre‐adaptation). Main conclusions Our results provide evidence that the high vigour of this major invasive species in its introduced range is probably due to both a response to more favourable conditions and rapid evolution.

Regional differences in clonal Japanese knotweed revealed by chemometrics-linked attenuated total reflection Fourier-transform infrared spectroscopy

“…Additionally, in North America invasion of diverse habitats by few Japanese knotweed genotypes has been correlated with epigenetic differentiation, with the conclusion that some epigenetic loci may respond to local microhabitat conditions [ 23 ]. Japanese knotweed from different sources grown in the same greenhouse have been known to possess differing levels of physiological vigour, with the French variant growing more vigorously than its Japanese counterpart, suggesting either a rapid evolution or pre-adaptation [ 128 ].…”

Cross-continental variation of herbivore resistance in a global plant invader

“…No difference or even higher resistance of invasive populations are also found in other invasive species within common garden experiment, for example, in Chromolaena odorata (Liao et al, 2014), Brassica nigra (Oduor et al, 2011), and in Verbascum Thapsus (Endriss et al, 2018). Similar or higher resistance and performance of introduced Japanese populations of R. japonica was also documented by Rouifed et al (2018), in which they found that introduced populations did not differ in composition of secondary metabolites, stem stiffness, leaf thickness, aboveground biomass and height, but were higher in leaf toughness and belowground biomass to the native R. japonica populations when grown under similar condition in the introduced range. As the Japanese populations used in our experiments were likely from the source region of the introduced European and North American populations, our results thus provide evidence that the introduction of certain genotypes (i.e.…”

“…It compared only five native Japanese and five invasive French populations in a common garden in the introduced range, but it also found that introduced populations did not differ in their composition of secondary metabolites, stem stiffness and leaf thickness, but that they had even higher leaf toughness than native Japanese populations. As the Japanese populations used in our experiments – as well as those used in Rouifed et al . (2018) – were from the putative source region of knotweed introductions to Europe and North America, our results thus indicate that the introduction of plants with particular resistance profiles, rather than post-invasion evolution, underlies the trait divergence between the native and introduced range, and may have played a role in the invasion success of R. japonica .…”

“…with Chromolaena odorata (Liao et al ., 2014), Brassica nigra (Oduor et al ., 2011), or Verbascum thapsus (Endriss et al ., 2018). We are only aware of one previous common garden study with native and introduced populations of R. japonica (Rouifed et al . 2018).…”

“…with Chromolaena odorata (Liao et al, 2014), Brassica nigra (Oduor et al, 2011), or Verbascum thapsus (Endriss et al, 2018). We are only aware of one previous common garden study with native and introduced populations of R. japonica (Rouifed et al 2018). It compared only five native Japanese and five invasive French populations in a common garden in the introduced range, but it also found that introduced populations did not differ in their composition of secondary metabolites, stem stiffness and leaf thickness, but that they had even higher leaf toughness than native Japanese populations.…”