Adaptive Evolution Of Defense Strategy Of Invasive Alien Plant Ambrosia Artemisiifolia And Its Ecological Consequence

Many countries have adopted biological control to manage invasive alien plants.However,biological control not only cause ecological negative impacts on invasive alien plants,but also exert herbivory pressure to drive the adaptive evolution of invasive alien plants.To date,most studies have focused on resistance or traits related resistance of invasive alien plants after biological control,while tolerance has received little attention.Moreover,the adaptive evolution of invasive alien plants after biological control may in turn affect the performance of herbivores,which may elicit profound effect on efficiency of biological control,while such ecological feedback has been overlooked.Therefore,examining the adaptive evolution of different defense strategies of invasive alien plants after biological control and their ecological feedbacks to efficiency of biological control are essential to understand the coevolution of plants and herbivories and help to provide an theoretical basis for the improvement of future biological control.In this study,we examined the effects of biological control on the adaptive evolution of resistance and tolerance of A.artemisiifolia and the feedback of adaptive evolution to the specialist Ophraella communa(Coleoptera: Chrysomelidae).Furthermore,we also included Spodoptera litura(Lepidoptera: Noctuidae)as an control in this study since it is a generalist and also feeds on A.artemisiifolia in China.The results are as follows:1.Adaptive evolution of resistance after biological controlWe conducted a bioassay to compare the growth of O.communa and S.litura on controlled and uncontrolled A.artemisiifolia populations.The results showed that there was no significant difference in the growth rate of O.communa between the two types of populations,and S.litura exhibited same patterns.The growth rates of O.communa and S.litura did not show significant correlation with the biocontrol time.Furthermore,we measured the concentration of chlorogenic acid(chemical defense)and the density of trichome(physical defense).We found that there were no significant differences in chlorogenic acid and trichome between controlled and uncontrolled A.artemisiifolia populations.Similarly,the chlorogenic acid and trichome were not significantly correlated with the biocontrol time.Taken together,our results indicated that resistance of A.artemisiifolia has not changed after biological control.2.Adaptive evolution of tolerance after biological controlWe conducted a greenhouse experiment to compare the regrowth ability of controlled and uncontrolled A.artemisiifolia populations after feeding by O.communa and S.litura.The results showed that there was no significant difference in tolerance score between the two types of A.artemisiifolia populations after O.communa or S.litura herbivory.Furthermore,the tolerance score had no significant correlation with the biocontrol time.These results indicated that the tolerance of A.artemisiifolia has not undergone significant adaptive evolution after biological control.3.The effect of adaptive evolution of invasive alien plants on the effectiveness of biological controlWe conducted a common garden experiment to examined the growth of controlled and uncontrolled A.artemisiifolia populations when O.communa was released.The results showed that aboveground biomass of controlled A.artemisiifolia populations was significantly higher than that of the uncontrolled populations.Moreover,the aboveground biomass of A.artemisiifolia was significantly positively correlated with the biocontrol time.Our results suggested that the growth of A.artemisiifolia has undergone adaptive evolution after biological control,which has weakened the efficiency of biological control.By combining bioassays,chemical analyses,greenhouse and common garden experiments,our study provides clear evidence that biocontrol did not elicit adaptive evolution in resistance and tolerance of invasive alien plant A.artemisiifolia,but enhanced growth rate of A.artemisiifolia.Thus,it is critical to re-evaluate the comprehensive impact of biological control on invasive alien plants in the future.