Invasive plants do not display greater phenotypic plasticity than their native or non‐invasive counterparts: a meta‐analysis

Phenotypic plasticity is commonly considered as a trait associated with invasiveness in alien plants because it may enhance the ability of plants to occupy a wide range of environments. Although the evidence of greater phenotypic plasticity in invasive plants is considerable, it is not yet conclusive. We used a meta‐analysis approach to evaluate whether invasive plant species show greater phenotypic plasticity than their native or non‐invasive counterparts. The outcome of such interspecific comparisons may be biased when phylogenetic relatedness is not taken into account. Consequently, species pairs belonged to the same genus, tribe or family. The meta‐analysis included 93 records from 35 studies reporting plastic responses to light, nutrients, water, CO₂, herbivory and support availability. Contrary to what is often assumed, overall, phenotypic plasticity was similar between invasive plants and native or non‐invasive closely related species. The same result was found when separate analyses were conducted for trait plasticity to nutrients, light and water availability. Thus, invasive plant species and their native or non‐invasive counterparts are equally capable of displaying functional responses to environmental heterogeneity. The colonization of a wide range of environments by invasive plants could be due to their capacity to undergo adaptive ecotypic differentiation rather than to their ability to display plastic responses. Alternatively, phenotypic plasticity might play a role in plant invasion, but only during the initial phases, when tolerance of the novel environment is essential for plant survival. Afterwards, once alien plants are identified as invaders, the magnitude of phenotypic plasticity might be reduced after selection of the optimum phenotypes in each habitat. The identification of plant traits that consistently predict invasiveness might be a futile task because different traits favor invasiveness in different environments. Approaches at the local scale, focusing on the ecology of specific invasive plants, could be more fruitful than global macro‐analyses.