Importance of invasion mechanisms varies with abiotic context and plant invader growth form

Abstract

Many invasion hypotheses propose biotic interactions as the main mechanismto explain non-native species' success. Despite the evidence that the strength of biotic interactions varies with abiotic context, it remains unclear whether the importance of the different mechanisms proposed to explain invasion predictably varies with the abiotic context and whether this variation is consistent across different growth forms.2. We reviewed studies at a global scale to evaluate whether evapotranspiration, latitude, precipitation and temperature influence the importance of disturbance, enemy release, facilitation, and novel weapons mechanisms to explain non-native plant invasions. In total, we calculated 171 effect sizes for ~300 non-native plant species covering a wide range of environmental conditions and growth forms.3. Environmental context and plant growth form influenced the role played by each invasion mechanism. The importance of disturbance in facilitating invasion exhibited a quadratic relationship with latitude and temperature, and decreased with increasing precipitation. In mixed communities and trees, disturbance was mediated by either evapotranspiration, latitude, precipitation or temperature.Enemy release exhibited a quadratic relationship with evapotranspiration, latitude and precipitation, and it was positively related to temperature. The importance of enemy release was also contingent on growth form and was highly context-dependent. Enemy release responses for grasses, and trees were modulated by either evapotranspiration, latitude, precipitation or temperature. The importance of facilitation decreased with increasing temperature. In forbs, facilitation decreased with evapotranspiration and temperature. The importance of novel weapons was more strongly confirmed for studies conducted at lower evapotranspiration, precipitation and higher latitudes, and exhibited a quadratic relationship with temperature. Synthesis.Our results show that environmental conditions not only filter nonnative species depending on physiological tolerances but may also influence the importance of invasion mechanisms.

A mechanistic framework of enemy release

“…For example, of the 85 biogeographic comparisons compiled by Jeschke and Heger (2018) in their review of evidence for the ERH (http://hi-knowledge.org), just 16 of 85 (19%) considered performance, with 7 of those 16 (44%) supporting the ERH. Furthermore, performance is influenced not just by enemy richness or abundance, but by the effect of those enemies, and other biotic and abiotic factors (Chiuffo et al., 2022). With a small number of studies testing Step 3, and no clear framework to integrate the range of potential influences on performance, it is extremely difficult to determine why the ERH has support in some cases but not others.…”

“…Data and code supporting the manuscript are available in Zenodo: https://doi.org/10.5281/zenodo.8403569 (Brian, 2023).…”

“…(2009) found no release from soil‐borne enemies. The context in which a test is carried out could explain why the occurrence or strength of enemy release can vary between studies (Catford et al., 2022; Chiuffo et al., 2022). However, relevant contexts are rarely reported in ERH studies, leaving no clear path for synthesising circumstances where enemy release promotes exotic success and potential invasive impacts.…”

“…The two studies reached opposite conclusions: Reinhart et al (2003) showed that release from belowground pathogens promoted exotic success, while te Beest et al (2009) found no release from soil-borne enemies. The context in which a test is carried out could explain why the occurrence or strength of enemy release can vary between studies (Catford et al, 2022;Chiuffo…”

Timing of invasive species removal influences nonnative biotic resistance and trajectories of community reassembly

“…In the same way that interactions do not occur isolated, they take place within an environmental context whereby resource availability or environmental harshness can determine the strength of interactions and even their sign (Chiuffo et al, 2022; Daehler, 2003; Sheppard & Burns, 2014). Furthermore, the environmental setting (e.g.…”