Can limiting similarity increase invasion resistance? A meta‐analysis of experimental studies

Abstract

Synthesis We used meta‐analyses to examine experimental evidence that functional similarity between invaders and resident communities reduces invasion. We synthesized evidence from studies that experimentally added seed to resident communities in which the functional group composition had been manipulated. We found communities containing functionally similar resident species reduced invasion of forb but not grass invaders. However, experimental design dramatically influenced the results – with evidence for limiting similarity only found in artificially assembled communities, and not when studies used functional group removal from more ‘natural communities’. We suggest that functional group similarity plays a limited role in biotic resistance in established communities. The principle of limiting similarity suggests that species must be functionally different to coexist; based on the assumption that inter‐specific competition should be greatest between functionally similar species. There has been controversy over the generality of this assembly rule for plant communities with some studies finding evidence for limiting similarity and others not. One approach to testing this is to examine the ‘invasion’ success of species into communities in which the functional group composition has been manipulated. Using a meta‐analysis approach, we examined the generality of limiting similarity for plant communities based on published experimental studies. We asked – is establishment of an invading species less successful if it belongs to a functional group that is already present in the community compared to a community in which that functional group is absent? We explored separately colonisation (i.e. germination, establishment or seedling survival) and performance (i.e. biomass, cover or growth) of different functional groups (forbs and grasses) and experimental designs (removal experiments of more or less natural communities and synthetic‐assemblage experiments). We found that communities containing functionally similar resident species did reduce invader colonisation and performance of forb invaders, but did not reduce colonisation or performance of grass invaders. Evidence in support of limiting similarity was only detected in synthetic‐assemblage experiments and not when studies used functional group removal from ‘natural’ communities. Functional similarity is an important aspect of biotic resistance for forb invaders, but was only found in artificial communities. This has implications for restoration ecology especially when communities are built de novo. However, we suggest that limiting similarity plays a limited role in biotic resistance, because no evidence was detected in established communities.

Community assembly by limiting similarity vs. competitive hierarchies: testing the consequences of dispersion of individual traits

“…This is consistent with a number of recent empirical findings which show absent or very weak signatures of limiting similarity (e.g. Kunstler et al 2012;Bennett et al 2013;Price & P€ artel 2013).…”

Advances in restoration ecology: rising to the challenges of the coming decades

“…Funk et al (2008) suggested that strategically increasing the abundance of native plant species with functional traits similar to nonnative plant species can increase biotic resistance to invasion, through limiting similarity. However, a meta-analysis of experimental studies testing the effect of functional similarity on invasion success, only found evidence for this in synthetic experimental assemblages, and not in more 'natural' removal experiments (Price and Pärtel 2013). Hence ''restoration through reassembly'' (Funk et al 2008) may only be useful as a guiding principle when communities are built de novo.…”

Functional group dominance and identity effects influence the magnitude of grassland invasion

“…In the study grassland, however, functional group biomass was pervasive in determining its ability to control expansion by established exotic species. Thus, life-form similarity did not emerge as a relevant aspect of invasion patterns in this removal experiment (Price & P€ artel 2013). Low compensatory responses to removal of dominant native grasses suggested that mechanisms other than resource competition, including temporal niche separation, recruitment limitation and facilitation, all influenced community dynamics (Stachowicz & Tilman 2005;Gilbert, Turkington & Srivastava 2009;Roscher et al 2009).…”

“…It has been argued that functional similarity between resident and invader species may influence invasion success (Fargione, Brown & Tilman 2003;Hooper & Dukes 2010;Price & P€ artel 2013). Accordingly, invasion would be more likely by species sharing the same functional group (or lifeform) with species being lost (Symstad 2000;Emery 2007;Mwangi et al 2007).…”

“…The loss of subordinate or rare species can create a heterogeneous mosaic of small canopy openings susceptible to colonization by exotic ruderals (Burke & Grime 1996;Lyons & Schwartz 2001). Indeed, resident species attributes other than biomass, such as growth form, phenology or rooting depth, can be important determinants of invasion (Stachowicz & Tilman 2005;Wolkovich & Cleland 2010;Price & P€ artel 2013). Interestingly, identity effects need not be restricted to rare taxa but may involve dominant species as well.…”