Plant invasions and the niche

Abstract

Summary1. For plant invaders, being different is often equated with being successful, yet the mechanistic connection remains unclear. 2. Classic niche theory predicts that invaders with niches distinct from the native flora should coexist with little interaction with native species, yet such invaders often have substantial impacts. Meanwhile, invaders that overlap in niche space with native species should either be repelled or dominate, yet these invaders often naturalize with little effect. Such discrepancies between theory and observation raise questions about how species differences influence invader establishment and impact. 3. Here, we review these issues in light of recent work on coexistence theory, which shows how niche and fitness differences between natives and invaders interact to determine invasion outcomes. We show how successful invader establishment depends on either a fitness advantage or niche difference from resident species, but that only the former allows invaders to become dominant. 4. By identifying the role of niche and fitness differences in leading invasion hypotheses, we unify their predictions for invasion success while highlighting new approaches for evaluating the importance of species differences for invasion. 5. Synthesis. Situating the invasion process within a recent coexistence framework broadens our understanding of invasion mechanisms and more tightly links problems in invasion ecology with our more general understanding of community dynamics.

Species coexistence: macroevolutionary relationships and the contingency of historical interactions

“…Our patterns of rapid predictable divergence in fitness differences but not stabilizing differences among species from different floras has been hypothesized [44], but has remained untested until now. Future work is needed to identify the traits that underlie stabilizing and fitness differences among non-native competitors.…”

Frequent burning promotes invasions of alien plants into a mesic African savanna

“…The explanation for this increased performance of alien forbs in plots exposed to regular annual and biennial fires is not clear, but may be attributed to different mechanisms. First, by killing or damaging dominant grass species and suppressing woody plant recruitment and growth (Furley et al 2008;Van Wilgen et al 2007), frequent fires may prevent their competitive dominance, thereby creating a window of opportunity for alien forbs to establish (Alpert 2006;Barney and Whitlow 2008;Frost et al 1985;MacDougall et al 2009;Shea and Chesson 2002). Second, frequent fires tend to create gaps in a plant assemblage suitable for colonisation by alien species, particularly those small-seeded forbs with high seed production and a relatively short life cycle (Sousa 1984).…”

Thermal sensitivity predicts the establishment success of nonnative species in a mesocosm warming experiment

“…Although physiological constraints (Dunson and Travis 1991) can hinder an organism's establishment, interactions with the existing biotawhether competitors, predators, parasites, or mutualists-further influence colonization ability (McPeek 1990, Miller et al 2002. Predicting the ability of a species to establish within an existing biological community remains a challenge (Dzialowski et al 2007, MacDougall et al 2009), due to the difficulties of assessing the importance of biotic interactions and then predicting how biotic interactions vary with the abiotic environment. For example, competition is important in determining the composition of biological communities, but the outcome of competitive interactions depends on local environmental conditions, including the external environment (e.g., temperature, UV radiation and precipitation) and other organisms present (Connell 1983, Chase et al 2002.…”