The community ecology of invasive species: where are we and what's next?

Abstract

Alien species are continually introduced in most regions of the world, but not all survive and coexist with the resident native species. Approaches analyzing the functional (or phylogenetic) similarity between invasive species and native communities are increasingly employed to infer the processes underlying successful invasions and to predict future invaders. The relatively simple conceptual foundations have made these approaches very appealing and therefore widely used, often leading to confusion and hampering generalizations. We undertook a comprehensive review and synthesis of the functional similarity approach in invasion community ecology to clarify its advantages and limitations, to summarize what has been learned thus far, and to suggest avenues for future improvement. We first present the methodological state of the art and provide general guidelines. Second, by organizing the published literature around seven key questions in invasion ecology we found cumulative evidence that: at large spatial scales phylogenetic relatedness of invasive and native species is a good predictor of invasion success, but a poor predictor of invasion impacts; at fine spatial scales, community resistance to invasion tends to increase with native species diversity and with similarity to the invaders, consistent with patterns emerging from biotic interactions. In general, the processes filtering invaders appear to vary across species’ invasion stage and along environmental gradients. Nonetheless, we found conflicting evidence for differences in community assembly processes between invasive and native species, and between the invader's native and adventive ranges. Finally, we propose four important avenues for overcoming some of the identified methodological and conceptual limitations of the approach, in particular by integrating observational and experimental analyses and by explicitly considering species’ demographic rates and complex biotic interactions. Although the functional similarity approach bears intrinsic limitations, it still offers many opportunities in invasion community ecology at large spatial scales.

Nonlinear effects of phylogenetic distance on early‐stage establishment of experimentally introduced plants in grassland communities

“…The shape of the relationship could result from the lack of intermediate DNNS values in this dataset (Figure ). Nevertheless, the lower seedling survival at high than at low DNNS values suggests that environmental filtering favours seedling survival of species that have a closely related species present in the resident community (Gallien & Carboni, ), and supports the preadaptation hypothesis. Alternatively, closely related species may not have similar environmental requirements to resident species per se, but instead result in more similar environmental conditions.…”

“…Preadaptation should operate both at small and large spatial scales, whereas competitive exclusion is likely to act only at the small spatial scales where organisms interact (Carl, Doktor, Schweiger, & Kühn, ). Therefore, when preadaptation (environmental filtering) and competitive exclusion both play a role, the highest establishment success may be at intermediate phylogenetic distances (Gallien & Carboni, ; Gallien, Carboni, & Tamara, ). To the best of our knowledge, such nonlinear relationships have not yet been tested (van Kleunen, Bossdorf, & Dawson, ).…”

Environmental resource deficit may drive the evolution of intraspecific trait variation in invasive plant populations

“…Inter‐annual CVs for CMD were calculated as indicators of moisture variability. Correlation analyses among climate variables, IPTV and IN were performed in R (< http://www.r-project.org >) via package ‘Hmisc’ (Harrell et al ).…”

“…When IPTV is larger, the opportunity for selection to act is increased (thus higher evolvability) (Espeland and Rice ), which may enable adaptive changes to novel environments encountered during invasion. The role of ITV/IPTV in plant community processes (Bolnick et al , Violle et al , Barabas et al 2016), especially at local scales (Albert et al , Siefert et al ), has re‐gained attention recently, and linking community ecology with invasive species traits has been emphasized to explain invasion success (Gallien and Carboni ). However, IPTV as a potentially important factor that modulates population evolvability, species interactions and invasion outcomes has seldom been explored experimentally, and the environmental driver of the evolution of IPTV is unclear.…”

Categorization of species as native or nonnative using DNA sequence signatures without a complete reference library

“…), and/or are more genetically distinct from native members of the community (Strauss et al. ), it is likely that the genetic distance to the nearest neighbor species in the collection might be greater for nonnative species then for native species (i.e., phylogenetic distance; see review by Gallien and Carboni ). Because the native/nonnative status of a species is often difficult to determine in natural communities, here we propose to use a training data set of known introduced and known endemic species with the assumption that introduced and endemic species might be at opposite ends of the native/nonnative spectrum and that if the above measures of genetic diversity are distinct between native and nonnative species, that they should be even more so between endemic and introduced species.…”