How much do phenotypic plasticity and local genetic variation contribute to phenotypic divergences along environmental gradients in widespread invasive plants? A meta‐analysis

Abstract

For introduced species that have spread across a wide distributional range, phenotypic plasticity (PLA) has often been proposed as an important contributor to invasion success, because it increases the survival rate during initial colonization. In contrast, local genetic variation (LOC) has also been proposed to be important, because it could allow invaders to evolve high performance in a new habitat. While evolutionary ecologists have long been interested in understanding genetic mechanisms that allow rapid colonization and spread of species, until recently experimental tests of these concepts have been limited. As a step towards generalization in our understanding of the importance of PLA and LOC, we review the current state of the literature on this topic using meta-analysis. Here, we focused on three fundamental questions: 1) which strategy, PLA or LOC, better explains the phenotypic divergences during invader range expansion across different environmental gradients? 2) Which species characteristics correlate with the occurrence of these different phenomena? And 3) does the detection of PLA versus LOC depend on the trait studied? Using meta-analysis we found that plasticity explained a higher proportion of phenotypic variation regardless of the environmental gradients studied or plant growth forms. PLA predominated in clonal, self-compatible and perennial species, while LOC predominated in annual species. The patterns were trait-dependent: LOC was significantly more important than PLA in phenology, while opposite patterns were found in fecundity and biomass allocation. The frequent simultaneous detection of PLA and genotypic variation in PLA among invasive populations suggested that PLA might benefit from LOC to some extent. Our results also indicate that the contribution of plasticity to the competitive advantages of invasive plants may be more informative than the level of plasticity itself.

Similarities between invaders and native species: Moving past Darwin's naturalization conundrum

“…Similarly, trait plasticity may enhance competitive responses if species can shift their root traits to avoid competition belowground or their leaf traits to competitively suppress their neighbors (Bennett, Riibak, Tamme, et al., ). Similar effects of trait plasticity can also affect biotic resistance experienced by invaders (Conti et al., ), although its importance may depend on the characteristics of the invading species (Liao et al., ) and the traits that exhibit plasticity (Godoy, Valladares, & Castro‐Díez, ). Regardless of its importance, incorporating trait plasticity in similarity–invasion models will likely remain challenging unless plasticity is treated as a trait.…”

Salt‐tolerant native plants have greater responses to other environments when compared to salt‐tolerant invasive plants

“…However, the incidences of exotic plants invading some rarely inhabited, stressful habitats have increased dramatically (Caño, Mendizabal, Baquero, & Herrera, ). The greater expansion potential of invasive compared with native species is often attributed to fast adaptive responses to stresses (Liao, D'Antonio, Chen, Huang, & Peng, ). Plants might evolve a stronger tolerance to one stressor in order to persist in a particular habitat (Ahmad, Ashraf, & Ali, ), and such evolution has been proposed to incur costs on plant performance (Bijlsma & Loeschcke, ; Lachmuth, Durka, & Schurr, ) and affect the responses to other stressors (Brenes‐Arguedas, Roddy, & Kursar, ).…”

Traits correlate with invasive success more than plasticity: A comparison of three Centaurea congeners

“…Furthermore, high plasticity levels are not necessarily associated with fitness gains (Davidson et al., 2011) and reaching a particular balance between plasticity and local trait adaptation could be key to invasive success (Liao, D'Antonio, Chen, Huang, & Peng, 2016). Rapid local adaptation by colonizing or invading species is an alternative to phenotypic plasticity for coping with new environmental conditions.…”

“…These results suggest that local adaptation might be a more common response to variable environments than adaptive phenotypic plasticity (Palacio‐López, Beckage, Scheiner, & Molofsky, 2015). A second meta‐analysis (Liao et al., 2016) suggested that phenotypic plasticity explained a higher proportion of phenotypic variation in clonal, self‐compatible, and perennial species, whereas local adaptation explained more phenotypic variation for annual species. Liao et al.…”