Exploring The Role Of Plant Fucntional Traits In Exotic Species Invasions Within A Biotic Interaction Framework

Non-native species invasions impose great threat to biodiversity and national security,and the number of non-native species increased rapidly in the world in the past 200 years.Thus,there is a pressing need to explore the invasion mechanisms to improve our ability to predict invasion risk and to manage invasive species.Increasing number of studies show that plant functional traits have profound effects on interspecific interactions and exotic plants invasions,and could be used to predict invasion risk of exotic plants.Most of existing studies,however,focus on comparison in functional traits and their responses to abiotic environmental variations between native and exotic plants.Thus,how plant functional traits affect biotic interactions and thus exotic plants invasion remina unclear.By combing manipulated experiments and field surveys,this study has explored the role of plant functional traits in plant invasions from the perspective of biotic interactions using common exotic and native plant species in China.Specially,this study has explored:1)when planted or occurred in the field individually,whether native vs.exotic plants differ in functional traits and recruit differing rhizosphere fungi,and whether functional traits and rhizphsere fungi are related?2)when occurred in complex biotic contents(e.g.,with interspecific competition),whether functional traits of native vs.exotic plants differ?If so,whether such difference confers competitive advantage for exotic plants.We obtained following main results:(1)There were no differences in most functional traits between individually-grown native vs.exotic plantsThe values of most tested functional traits(e.g.,total mass,stem height and resource allocation pattern),trade-offs between paired plant functional traits are similar between the tested exotic(71 species)and native(59 species)plants.The values of some leaf traits(e.g.,leaf dry matter contents,leaf area,the contents of nitrogen and carbon and their ratio)were significantly different between native plants and exotic plants.The values of most functional tratis are primarily shaped by plant evolutionary history,rather than by species origin(native vs.exotic),that the value of most functional tratis are more similar between phylogenetically close-related vs.distant-related plants.(2)Native and exotic plants recruit similar rhizosphere fungi when grown or occurred in the field individually,and regulated by functional traitsIn the field,the composition of rhizosphere fungi and the richness of overall and host-specific fungal OTUs were similar between co-occurring exotic(27 species)and native(26 species)plant species.The composition of plants rhizosphere fungi that varied across latitudes is primaly shaped by plant evolution rather than species origin(exotic vs.native)and abiotic environments(e.g.,climate and soil properties).The compositional dissimiarlty in rhizophere fungi between exotic plants is higher than that between native plants at middle latitudes.There is a clear correlation beween plant functional traits and mycorrhizae composition.In the greenhouse,the composition of rhizosphere fungi and the richness of overall and host-specific fungal OTUs were also similar between 8 pairs of phylogenetically-related native and exotic plants,which were primarily shaped by plant evolution.(3)Differing response of functional tratis to complex biotic context conferred competitive advantage for exotic plantsWhen planted in mixture in a common garden,on average exotic plants’individual aboveground mass and stem height were higher than those of native plants,but the relative performance of exotic vs.native plants varies among sampling sites.For instance,individual aboveground mass of exotic plants was higher than that of native plants for those sampled from Guangdong,Guangxi and Shandong,where native and exotic species sampled from Hunan,Hubei and Henan showed no differences in aboveground mass.In a common garden experiment conducted at Guilin and Zhenzhou using 7 exotic plants,aboveground herbivory had no effects on plant performance and increasing the number of conspecific individuals significantly increase exotic plants’ competitive effects on native species at only in Guilin.Taken together,our findings suggest that sharing similar functional traits and associated with soil biota might facilitate initial population establishments for exotic plants in new ranges,whereas differing reponses to biotic interactions(such as interspecific competition and intraspecific interactions)might confer competitive advantage for exotic plants which in turn promote their invasions.Moreover,these findings also indicate that the role of plant functional traits in exotic plants invasions might changes across space in response to changes in abiotic and biotic environment.Thus,it is necessary to consider biotic interactions in exploring the role of plant fuctional traits in exotic plants invasions across space.Our findings extend our understanding of how functional traits affect exotic plants invasions,the interaction between native soil microorganisms and exotic plants,and their evolution,and enrich the theory of invasion biology.