Effects Of Invasive Plants On Mycorrhizal Fungi Colonization And Its Mechanisms In Native Plants

With the acceleration of global economic development and trade integration,exotic plants invasion has become a critical issue that can not be ignored.Compared with the aboveground part of invasive plants,the underground part of invasive plants is relatively less explored.Exotic plants have diverse ways by which to invade the native plant communities in the invaded range,e.g.,the emergingly reported disruption of the mutualism relationship between native species and mycorrhizal fungi by invasive plants besides the widely reported high resource use efficiency associated with invasive plants.The mutualism of mycorrhizal fungi and plant roots is important for plant growth and development,and the destruction of this mutualism relationship has been considered as an important mechanism for the invasion of the exotic plant.Ecological strategies of plants are evolutionarily shaped in plant adaptation to the long term variation of growing environments.For example,the fast strategy vs.slow strategy is widely reported in terrestrial plants which is based on the of nvestment-benefit trade-off in plant resource foraging.Nevertheless,there are few studies have explore the impacts on mycorrhizal association in native plants by invasive plants with different fast vs.slow strategies.To fulfil this knowledge gap,we chose five exotic plants common in Liaoning Province,i.e.,X.strumarium,S.rostratum,A.trifida,A.retroflexus and G.quadriradiata,and four native plants that widely coexist with these invasive plants,i.e.,X.sibiricum,S.viridis,E.crusgalli and A.annua.Through pot experiments,we conducted the following three experiments regarding to exploring:(1)the effects of exotic plants with different ecological strategies on native plants mycorrhizal fungi;(2)whether the effects of exotic plant S.rostratum on native plant mycorrhizal fungi were affected by soil nutrients;(3)whether the effects of exotic plant G.quadriradiata on native plant mycorrhizal fungi varied with light level(The treatment is shade by 58%).We used microscopic method to determine the mycorrhizal colonization.Molecular composition and relative abundance of the fungi communities in roots of native plants were determined thehigh-throughput sequencing technology.The results were as follows:(1)Influence of exotic plants with different growth strategies on the colonization of mycorrhizal fungi in native plantsInvasive plants with larger aboveground biomass(i.e.,fast strategy)showed smaller impact on the mycorrhizal colonization of the native plants,X.sibiricum(P = 0.003).This is contrary to our expectation.In contrast,the larger biomass of the invasive plants(i.e.,fast strategy),the lower impacts of them on root nitrogen content of X.sibiricum(P = 0.011).The impact of invasive species on mycorrhizal colonization in X.sibiricum is negatively correlated with the impact of invasive plants on root nitrogen content for this native(R2 = 0.37,P = 0.015).Furthermore,for X.sibiricum,it was the change of root nitrogen content rather than of mycorrhizal colonization that was linked with aboveground biomass of the invasive plants(P = 0.017).The native plant,S.viridis,shared similar above pattern to X.sibiricum.However,mycorrhizal colonization and root nitrogen content of the other two native plants,E.crusgalli and A.annua,had no above patterns and also showed no correlation with the aboveground biomass of the invasive plants,which might be related to the biomass allocation between root and shoot and the possible allelopathy of the invasive plants.(2)Effects of exotic plants with different growth strategies on the diversity and structure of native plant fungi communitiesFive invasive plants with different growth strategies can significantly increased the Alpha diversity index of fungi communities in roots of X.sibiricum and S.viridis(Chao1 index as an example),but did not affect the fungi diversity index of E.crusgalli and A.annua.For the composition of fungal community,the relative abundance of Ascomycota,Basidiomycota and Glomeromycota in A.annua was significantly affected by the invasive plants with different growth strategies.Invasive plant A.retroflexus(slow strategy)is significantly increased relative abundance of Chytridiomycota in roots of E.crusgalli.These invasive plants had no effect on the relative abundance of fungi communities in roots of X.sibiricum and S.viridis.NMDS(non-metric multidimensional scaling)analysis showed that five invasive plants with different growth strategies significantly affect the fungi community structure of A.annua,but did not affect the fungi community structure for roots of X.sibiricum,S.viridis and E.crusgalli.Together,our result in this section suggested that the influence of invasive plants on the fungi community structure of native species varied for different native plants.(3)Effects of invasive plant S.rostratum on the diversity and structure of four native species fungi communities under different soil fertility.In fertile soils,S.rostratum can increased the Alpha diversity index of E.crusgalli fungi community(Shannon index as an example).However,under infertile soils,S.rostratum increased Shannon index of S.viridis and E.crusgalli.As for fungi community composition,under fertile soils,S.rostratum reduced the relative abundance of Sordariales in roots of S.viridis and Ascomycota in roots of E.crusgalli,increased the relative abundance of unclassified-k-Fungi in roots of E.crusgalli,Ascomycota and Basidiomycota in roots of A.annua,and decreased the relative abundance of Glomerycota in roots of A.annua.Under infertile soils,S.rostratum increased the relative abundance of unclassified-k-Fungi in roots of X.sibiricum and A.annua,and the relative abundance of Sordariales,unclassified-c-Sordariomycotes in roots of S.viridis and Ascomycota in roots of E.crusgalli,but increased the relative abundance of Glomeromycota and unclassified-k-Fungi in roots of E.crusgalli.NMDS analysis showed that in fertile soils,S.rostratum significantly change the fungi community structure for roots of A.annua,but did not affect the fungi community structure for roots of X.sibiricum,S.viridis,and E.crusgalli.Under infertile soils,S.rostratum significantly changed the fungi community structure for roots of X.sibiricum,S.viridis and E.crusgalli,but did not affect the fungi community structure for roots of A.annua.The results suggested that the effect of S.rostratum was more common under infertile soils on fungi community in the root of native plants.(4)Effects of native plant G.quadriradiata on the diversity and structure of four native plants fungi communities under different light conditionsIn un-shaded condition,G.quadriradiata increased Shannon index of fungi community in roots of X.sibiricum,but decreased Shannon index in roots of X.sibiricum under shade condition,and increased Shannon index in roots of E.crusgalli.For fungi community composition,in un-shaded condition,G.quadriradiata reduced the relative abundance of Glomeromycota in roots of A.annua.However,under shade condition,G.quadriradiata reduced the relative abundance of unclassified-k-Fungi in roots of X.sibiricum and S.viridis,and increased the relative abundance of Ascomycota and Zygomycota in roots of S.viridis.NMDS analysis showed that in un-shaded condition,G.quadriradiata significantly change the fungi community structure for roots of A.annua,but did not change the fungi community structure for roots of X.sibiricum,S.viridis and E.crusgalli.Under shade condition,G.quadriradiata significantly changed the fungi community structure for roots of X.sibiricum and S.viridi,but did not change the fungi community structure for roots of E.crusgalli.and A.annua.The results suggested that the influence of G.quadriradiata on the diversity and community composition of native plant fungi was regulate by light and also varied with the native species.In summary,the effects of invasive plants on mycorrhizal colonization,fungi community diversity and structure of native plants were influenced by the ecological strategies of exotic plants(fast strategy vs.slow strategy),soil fertility,light conditions and identity of the native species.This study will greatly promote our knowledge on the relationship between the mutulasim of native plants and invasive plant invasion as well as deepening our understanding about the diverse mechanisms of invasive plant invasion.Moreover,results of this study are instructive for the strategies taken to control of plant invasion.