The stability and variability in the genetic variance covariance-matrix (G-matrix) in plant resistance, and its role in the evolution of invasive plants has been largely overlooked. We conducted a reciprocal transplant experiment of tall goldenrod, Solidago altissima with multiple replicates within its native range (USA) and the introduced range (Japan) to explore the differences in the phenotypic traits and G-matrix of its resistance to herbivores between and within the countries.
Results/Conclusions
The Japanese plants were more resistant to the lace bug, Corythucha marmorata, which had recently invaded Japan, but were more susceptible to other herbivorous insects compared to the USA plants. Plant resistance to lace bugs was negatively correlated with the resistance to other herbivorous insects. The G-matrix reflecting this trade-off between plant resistances was stable between the plant-origin countries. Thus, S. altissima in Japan may be more susceptible to other herbivorous insects, but more resistant to lace bug herbivory as the result of allocation differences between native and invaded ranges. We also found that the plant resistances varied among gardens and populations within the countries, and G-matrices of plant resistances changed due to environmental differences. These results suggest that the flexibility in the genetic basis of resistance may help to protect the plant against numerous herbivore species without changing its genetic architecture, which may lead to the rapid adaptation of resistance in invasive plants. The environment in which the plant is growing also has a critical effect on plant resistance, and it should be considered in order to understand the evolutionary ecology of invasive plants.