Invasion mechanisms of Solidago canadensis L.:a review

Invasion of habitats by non-native species is one of the major factors that threaten global biodiversity and ecosystem functioning.China is becoming one of the most severely invaded countries in the world with increasing frequency of deliberate species introduction,international tourism and worldwide trade of agricultural products.A comprehensive understanding of invasion process and involved mechanism is very necessary to avoid the outbreak of invasive species and prevent new invasion.Solidago canadensis L,the worldwide invader with a invasion history over 70 years in China,has been extensively studied in the last decades.However,few studies concerned the persistent and profound impacts on local environment induced by invasion,and their feedbacks on subsequent invasion and plant community dynamics.Here,we reviewed the successful invasion mechanisms of S.canadensis from its biological characteristics,invasibility of the introduced range,allelopathic effect and plant-soil feedbacks based on novel interests and recent advancements,analyzed and evaluated the inherent relations between four aspects above.It suggested that invasion was a complicated biological process that involved multitrophic interactions of herbivores,carnivores,plants and decomposers,and a result of interactions between multiple mechanisms,among which the most far reaching reason was disturbance by human activities.The strong vegetative propagules produced by rhizome of S.canadensis strengthened its population established in invaded habitat,and the numerous fertile offspring expanded new habitat through wind dispersal.The high phenotype plasticity to resource fluctuation and high tolerance to stress conditions offered extra advantages over local competitors.These extrinsic performance could partially be explained by intrinsic features as S.canadensis was a polyploid complex and characterized by high genetic diversity.Moreover,the strong allelopathic effects on native plants and soil borne pathogens significantly inhibited potential antagonists,which undoubtedly further extended its dominance.Susceptibility of the introduced range resulted from appropriate climate,low biotic resistance and strong human disturbance provided favorable conditions for invasion.Besides,facilitated by mycorrhizal mutualism also played an important role in the invasion of S.canadensis.Community structure of arbuscular mycorrhizal fungi was changed in a way that favored S.canadensis more than native host plants.The mechanism of host preference remained unclear and represented an intriguing field that awaited to be intensively studied.Up to now,however,enemy release from goldenrod specific gallmaker and other pathogens in China did not show any positive impacts on its growth and reproduction.Although parasitized by Cuscuta japonica exhibited an obvious biological control potential,its ecological risks need to be further examined and evaluated before extensive application.Prospects for the study of S.canadensis in the future were proposed with emphases on(1) isolation,structure determination and in situ acting mechanism illumination of allelochemicals;(2) establishment and improvement of database,population dynamic and spreading tendency prediction using mathematical models;(3) long term monitoring on post invasion environmental changes,study on functions of S.canadensis in ecosystem and co-evolution with local organisms and(4) proper utilization,effective control and eradication method of S.canadensis.