Abstract
Phenotypic plasticity is a key mechanism associated with the spread of exotic plants and previous studies have found that invasive species are generally more plastic than co-occurring species. Comparatively, the evolution of phenotypic plasticity in plant invasion has received less attention, and in particular, the genetic basis of plasticity is largely unexamined. Native from North America, Acer negundo L. is aggressively impacting the riparian forests of southern and eastern Europe thanks to higher plasticity relative to co-occurring native species. We therefore tested here whether invasive populations have evolved increased plasticity since introduction. The performance of 1152 seedlings from 8 native and 8 invasive populations was compared in response to nutrient availability. Irrespective of nutrients, invasive populations had higher growth and greater allocation to above-ground biomass relative to their native conspecifics. More importantly, invasive genotypes did not show increased plasticity in any of the 20 traits examined. This result suggests that the high magnitude of plasticity to nutrient variation of invasive seedlings might be pre-adapted in the native range. Invasiveness of A. negundo could be explained by higher mean values of traits due to genetic differentiation rather than by evolution of increased plasticity.
Highlights
Phenotypic plasticity has been widely recognized as an important feature for plants to cope with environmental changes [1,2]
Davidson et al [21] recently synthesized this work via a metaanalysis of 75 pairs of invasive/native species concluding that invasive species do express greater phenotypic plasticity than native species irrespective of the response traits measured
There was no significant difference in maximum assimilation rates (Aarea and Amass; Fig. 1C), and invasive seedlings had lower leaf nitrogen contents (Narea and Nmass; Fig. 1D) and greater PNUE (Table 2)
Summary
Phenotypic plasticity has been widely recognized as an important feature for plants to cope with environmental changes [1,2]. Phenotypic plasticity has been classified as a major determinant of the success of invasive species by increasing fitness relative to native species in recipient communities [11,12,13]. Davidson et al [21] recently synthesized this work via a metaanalysis of 75 pairs of invasive/native species concluding that invasive species do express greater phenotypic plasticity than native species irrespective of the response traits measured. There are instances that did not support this pattern [22,23,24,25], and it has been suggested that the success and fitness advantage of invasive species can be mediated by the expression of constant higher mean trait values across different environments and not necessarily by the plasticity of these traits [26,27,28,29]. Invasive species frequently possess higher trait values for growth rate [30,31,32], lower leaf mass per area [30,33,34], and advanced leaf unfolding and flowering periods [35,36,37]
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