Plant invasion alters trait composition and diversity across habitats

Abstract

Increased globalization has accelerated the movement of species around the world. Many of these nonnative species have the potential to profoundly alter ecosystems. The mechanisms underpinning this impact are often poorly understood, and traits are often overlooked when trying to understand and predict the impacts of species invasions on communities. We conducted an observational field experiment in Canada's first National Urban Park, where we collected trait data for seven different functional traits (height, stem width, specific leaf area, leaf percent nitrogen, and leaf percent carbon) across an abundance gradient of the invasive Vincetoxicum rossicum in open meadow and understory habitats. We assessed invasion impacts on communities, and associated mechanisms, by examining three complementary functional trait measures: community‐weighted mean, range of trait values, and species’ distances to the invader in trait space. We found that V. rossicum invasion significantly altered the functional structure of herbaceous plant communities. In both habitats V. rossicum changed the community‐weighted means, causing invaded communities to become increasingly similar in their functional structure. In addition, V. rossicum also reduced the trait ranges for a majority of traits indicating that species are being deterministically excluded in invaded communities. Further, we observed different trends in the meadow and understory habitats: In the understory, resident species that were more similar to V. rossicum in multivariate trait space were excluded more, however this was not the case in the meadow habitat. This suggests that V. rossicum alters communities uniquely in each habitat, in part by creating a filter in which only certain resident species are able to persist. This filtering process causes a nonrandom reduction in species' abundances, which in turn would be expected to alter how the invaded ecosystems function. Using trait‐based frameworks leads to better understanding and prediction of invasion impacts. This novel framework can also be used in restoration practices to understand how invasion impacts communities and to reassemble communities after invasive species management.

Invasive dominance and resident diversity: unpacking the impact of plant invasion on biodiversity and ecosystem function

“…Leaf nitrogen content (LNC) and leaf carbon content (LCC) (mass of nitrogen and carbon per unit dry leaf mass, respectively) were quantified as averages for single species based on 17 replicates per species, with 12 of the 17 replicates added as supplementary data using the data set from Sodhi et al (2019). LNC and LCC were determined using the Thermo-Fisher EA 2000 elemental analyzer (Thermo-Fisher, Waltham, Massachusetts, USA) in the in TRACES (Teaching and Research in Analytical Chemical and Environmental Science) lab at the University of Toronto-Scarborough.…”

“…It is often asked whether it is an invasive species' relative uniqueness or similarity that can explain their establishment and subsequent dominance (i.e., Darwin's “naturalization conundrum”; Darwin 1859, Cadotte et al 2018, Sodhi et al 2019), and there is evidence on both sides. Some cases have shown that the traits of invasive species tend to be similar to those of resident communities (Cadotte et al 2018, Sheppard et al 2018), while others have found the opposite (Ordonez et al 2010, Gallien and Carboni 2017).…”

“…Such a finding supports the hypothesis put forth by MacDougall et al (2009) who, using Chesson's (2000) coexistence framework, contend that nonnative species that exhibit higher fitness and high niche overlap with native species are likely to have the greatest impact on the diversity of resident communities. Thus, in cases where an invasive species' high fitness has resulted in both reduced diversity and functional homogenization of invaded plant communities (e.g., Sodhi et al 2019), we should see an invader‐driven “dominance effect” that can result in increased ecosystem functioning in highly invaded communities (Cadotte 2017, Flombaum et al 2017). However, this dominance effect then comes at the expense of niche‐based species complementarity that explains why diversity per se increases function.…”

Urbanization and plant invasion alter the structure of litter microarthropod communities

“…beta diversity, community assembly, dog-strangling vine, ecological traits, functional diversity, mites, soil mesofauna, urban forests communities (Sodhi, Livingstone, Carboni, & Cadotte, 2019).…”

Functional niche differences between native and invasive tree species from the southern Brazilian mixed forest

“…may also be susceptible to invasion. When a community is invaded, non-native species may become dominant by replacing native ones through limiting similarity process (MacDougall et al 2009), then causing biodiversity loss (Bellard et al 2016) and functional composition changes (Villà et al 2011, Sodhi et al 2019.…”