Phenotypic plasticity as a clue for invasion success of the submerged aquatic plant Elodea nuttallii

Abstract

Two closely related alien submerged aquatic plants were introduced into Europe. The new invader (Elodea nuttallii) gradually displaced E. canadensis even at sites where the latter was well established. The aim of the study was to evaluate the combined effects of environmental factors on several phenotypic characteristics of the two Elodea species, and to relate these phenotypic characteristics to the invasion success of E. nuttallii over E. canadensis.• In a factorial design, Elodea plants were grown in aquaria containing five different nitrogen concentrations and incubated at five different light intensities. We used six functional traits (apical shoot RGR), total shoot RGR, relative elongation, root length, lateral spread, branching degree) to measure the environmental response of the species. We calculated plasticity indices to express the phenotypic differences between species.• Light and nitrogen jointly triggered the development of phenotypic characteristics that make E. nuttallii a more successful invader in eutrophic waters than E. canadensis. The stronger invader showed a wider range of phenotypic plasticity. The apical elongation was the main difference between the two species, with E. nuttallii being more than two times longer than E. canadensis. E. canadensis formed dense side shoots even under high shade and low nitrogen levels, whereas E. nuttallii required higher light and nitrogen levels.• We found that under more eutrophic conditions, E. nuttallii reach the water surface sooner than E. canadensis and through intensive branching outcompetes all other plants including E. canadensis. Our findings support the theory that more successful invaders have wider phenotypic plasticity.

Friends of mine: An invasive freshwater mussel facilitates growth of invasive macrophytes and mediates their competitive interactions

“…Given that regeneration of E. nuttallii is higher than E. canadensis in the spring, and the latter is thought to have a weaker ability to compete for light (Barrat‐Segretain & Elger, ), the former may have a competitive advantage where the species co‐occur (Barrat‐Segretain et al, ). Szabó, Peeters, Várbíró, Borics, and Lukács () found that increasing levels of light and nitrogen elicited phenotypic responses such as stem elongation in E. nuttallii that were far greater than that of E. canadensis . They also found that under eutrophic conditions, E. nuttallii branched rapidly and reached the surface sooner than E. canadensis, thereby shading out the weaker invader and other aquatic plants.…”

Greater Performance of Exotic Elodea nuttallii in Response to Water Level May Make It a Better Invader Than Exotic Egeria densa During Winter and Spring

“…The number of invaders (propagule pressure) is one of the traits that influence the ability of species to invade new communities (Lonsdale, 1999; Xie et al, 2013). Furthermore, E. nuttallii may produce a canopy shading out and inhibiting other species due to its shoot length (Barrat-segretain and Elger, 2004); a similar study suggested that E. nuttallii invests more in shoot elongation than E. canadensis and thus has a greater advantage for light capture (Szabó et al, 2019). We suggested that the earlier the start of the vegetative period, the higher the capability for vegetative reproduction, and a greater shoot length might contribute to E. nuttallii being more invasive than E. densa during winter and spring.…”

Alien Advantage in Endozoochorous Seed Dispersal of Aquatic Plants

“…if seeds arrived in an early season. This combined with the faster growth rate and higher trait plasticity of alien species can ensure their overall competitive superiority (Ruprecht et al 2014;Szabó et al 2019). According to our results, gut passage did not affect the plasticity of germination time, however we need more information on its dependence on environmental variables.…”