Marina Golivets1,2 and Kimberly F. Wallin1,3
1Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, VT, USA
2Helmholtz Centre for Environmental Research – UFZ, Halle, Germany
3USDA Forest Service, Northern Research Station, Burlington, VT, USA
High competitive ability has often been invoked as a key determinant of invasion success and ecological impacts of non-native plants. Yet our understanding of the strategies that non-natives use to gain competitive dominance remains limited. Particularly, it is unknown whether the two non-mutually exclusive competitive strategies, neighbour suppression and neighbour tolerance, are equally important for the competitive advantage of non-native plants. We analyzed data from 192 peer-reviewed studies on pairwise plant competition within a Bayesian multilevel meta-analytic framework. We found that non-native plants outperform their native counterparts due to high tolerance of competition, as opposed to strong suppressive ability. Competitive tolerance ability of non-native plants was driven by neighbour’s origin and was expressed in response to a heterospecific native but not heterospecific non-native neighbour. In contrast to natives, non-native species were not more suppressed by hetero- vs. conspecific neighbours, which was likely partially due to higher intensity intraspecific competition among the non-natives. Heterogeneity in the data was primarily associated with methodological differences among studies and not with phylogenetic relatedness among species. Altogether, this synthesis demonstrates that non-native plants are competitively distinct from native plants and challenges the common notion that neighbour suppression is the primary strategy for plant invasion success.