Plasticity in salt tolerance traits allows for invasion of novel habitat by Japanese knotweed s. l. (Fallopia japonica and F.×bohemica, Polygonaceae)

Abstract

Japanese knotweeds are among the most invasive organisms in the world. Their recent expansion into salt marsh habitat provides a unique opportunity to investigate how invasives establish in new environments. We used morphology, cytology, and AFLP genotyping to identify taxa and clonal diversity in roadside and salt marsh populations. We conducted a greenhouse study to determine the ability to tolerate salt and whether salt marsh populations are more salt tolerant than roadside populations as measured by the efficiency of PSII, leaf area, succulence, height, root-to-shoot ratio, and total biomass. Clonal diversity was extremely low with one F. japonica clone and five F. ×bohemica genotypes. The two taxa were significantly different in several traits, but did not vary in biomass or plasticity of any trait. All traits were highly plastic in response to salinity, but differed significantly among genets. Despite this variation, plants from the salt marsh habitats did not perform better in the salt treatment, suggesting that they are not better adapted to tolerate salt. Instead, our data support the hypothesis that plasticity in salt tolerance traits may allow these taxa to live in saline habitats without specific adaptation to tolerate salt.

Genetic and epigenetic variation in Spartina alterniflora following the Deepwater Horizon oil spill

“…These classic predictions are intuitive and often supported empirically (e.g., Clausen, Keck, & Hiesey, 1948). However, in some cases, data across a diversity of taxa show either no association of genetic differences with habitat (e.g., Richards, Hamrick, Donovan, & Mauricio, 2004; Foust et al., 2016; examples in Schmidt et al., 2008) or that low levels of molecular diversity are not associated with decreased phenotypic variation (Dlugosch & Parker, 2008; Richards et al., 2008). The disconnect between empirical findings and ecological theory suggests the possibility of additional, underexplored molecular mechanisms, such as epigenetic modifications, that mediate the relationship between phenotype and environment.…”

Variation of growth and functional traits of invasive knotweeds (Fallopia spp.) in Belgium

“…First, as FJ does not display genetic variation in Europe (Mandak et al 2004;Krebs et al 2009) any phenotypic variation must by definition have an environmental basis. Large phenotypic plasticity may be a key attribute of FJ (Richards et al 2008). Higher values of ramification rate and lower SLA in the site JJM compared to VER are ascribable to contrasting light conditions.…”

The influence of invasive Fallopia taxa on resident plant species in two river valleys (southern Poland)

“…Their rhizome system is very dense and can grow to 2 meters in depth [17]. Recent studies have shown that, apart from extensive vegetative growth, hybridization between the F. japonica and F. sachalinensis has created even more highly invasive genotypes of the hybrid F. ×bohemica that are able to establish themselves by seed [15,18,19].…”