PS 71-132
In the beginning: Phenotypic change in three invasive species through their first two centuries since introduction
Previous studies have demonstrated that most introduced species go through rapid phenotypic change during their first decades to centuries of being introduced to a new range. However, little is known about the trends these phenotypic changes follow from the beginning of the invasion through to the present day. Using herbarium specimens we track changes in the leaf area, leaf shape and plant height of three species (Epilobium ciliatum Raf., Senecio squalidus L. and Veronica persica Poir.) through their first ~200 years since introduction to the United Kingdom (U.K.). We also asked whether these species showed an initial lag phase in phenotypic change, and whether the species were still changing, or whether the species had reached a new equilibrium.
Results/Conclusions
All three species showed fluctuating direction and strength of phenotypic change through time. Linear models fit the data for the first 100 years after introduction better than did exponential curves, suggesting that none of our species underwent a lag phase. Finally, we found that all three species were still changing in at least one trait more than a hundred years after their introduction. All three species show fluctuating trajectory of phenotypic change and are still changing hundreds of years after introduction. This suggests that some invasive species are yet to demonstrate their full potential as invaders. Contrary to some expectations, invasive species do not have a lag in their phenotypic change at the beginning of the invasion. This is probably because the strongest selective pressures are exerted on them at the very beginning of their invasion, when the mismatch between their traits and the optimum for the new environment is greatest. Overall, our study shows that species are labile in the face of environmental change. Identifying the long term trajectories of invasive species’ phenotypic change during invasion provides important clues for their appropriate management.