A trait‐based approach across the native and invaded range to understand plant invasiveness and community impact

Abstract

Alien plant species invasiveness and impact on diversity (i.e. species richness and composition) can be driven by the altered competitive interactions experienced by the invader in its invaded range compared to its native range. Trait-based competition effects on invasiveness can be mediated through size-asymmetric competition, i.e. a trait suit of the invader that drives competitive dominance, and through 'niche differences', i.e. trait differentiation and thus minimized competition between invader and the invaded community. In terms of invasion impact, size-asymmetric competition is expected to result in competitive exclusion of co-occurring subordinate species, whereas 'niche differences' might result in competitive exclusion of the most functionally similar co-occurring species. Although observational work does not allow the full disentanglement of both trait-based effects, it does allow to verify the occurrence of expected theoretical trait patters. In this study, we explored the trait-based competition effects on invasiveness and diversity impact for Rosa rugosa in both its invaded range in Belgium and its native range in Japan, based on seven functional traits across 100 vegetation plots. Following the predictions for enhanced invasiveness, we found much lower functional overlap between R. rugosa and the co-occurring species in the invaded range compared to the native range. This likely also explains the absence of diversity impact in its native range. Despite the absence of changes in species richness in the invaded range, the invader did strongly impact species composition of invaded communities. This impact occurred through strong shade tolerance responses, suggesting size-asymmetric competition effects and cover loss of co-occurring dominant species, next to exclusion of co-occurring species most functionally similar to the invader; suggesting niche difference effects. In conclusion, this case-study illustrates how exploring functional trait patterns across a species native and invaded range can help in understanding how trait-based competition processes can affect invasiveness and community impact.

Invasion at the Edge: The Case of Rosa rugosa (Rosaceae) in Italy

“…Thus, R. rugosa showed traits conferring a higher competitive ability in its invaded range than its native range, such as a higher plant height [53] and more resource-conserving leaf traits (leaf P and K) [54]. In synthesis, many observations support the idea that R. rugosa has much lower functional overlap with the co-occurring species in the invaded range, and this pattern very likely enhances its invasiveness [52].…”

“…R. rugosa also has numerous impacts on ecosystem services in the invaded range: it increases nutrient concentrations, modifies microbial communities, and has negative effects on pollinators [52,[75][76][77]79].…”

“…The study by Helsen et al [51] also pointed out that R. rugosa had limited trait overlap with the invaded plant community where it is invasive: on average, it contributed to the functional space of the community introducing highly conservative leaf economic traits and strong light-competition related traits. A more recent study by Helsen et al [52] provided a comparison based on five functional traits related to the leaf economics spectrum (specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content (N), phosphorous content (P), potassium content (K)) and two traits related to light-competition ability (plant height and leaf area) between individuals of R. rugosa collected in Belgium (invaded range) and those surveyed in Japan (native range). It was observed that the species in Belgium had a higher plant height and lower leaf P and K than those growing in Japan (all other traits showed no differences between Belgium and Japan).…”

“…R. rugosa invasions are related to considerable changes in the soil environment of coastal dunes, resulting in increased concentration of nutrients such as C, N and P and modified microbial community structure [52,[75][76][77]. The increase in concentrations of some elements in soils under R. rugosa is presumed to be associated with differences in functional traits between the invader and native vegetation [53].…”

Effects of invasive Rosa rugosa on Baltic coastal dune communities depend on dune age

“…The response of local vegetation to the alien plant invasion may depend on the functional traits of the resident plants, but also on how they interact with the functional traits of the invader (Helsen et al 2021;Kaushik et al 2022). Unstable dunes where primary succession takes place are colonised by plant species adapted to hostile environments.…”