Effect Of Soil Biota On Alternanthera Philoxeriodes Invasion

Soil biota,microbe in particular,have profound impacts on plant population growth and community structure,and non-native plant invasions via plant-soil feedbacks.The composition of soil microbe could be affected by abiotic(e.g.,soil properties)and biotic(i.e.,plant species)factors,however,how foliar herbivore affect soil microbe and its feedbacks on plants,and how soil microbial community and its feedbacks on plant invasions change with latitude has little been explored.Here,we characterized the communities of fungi and bacteria in soils conditioned by the invasive plant Alternanthera philoxeroides and its native congener A.sessilis in the presence or absence of foliar herbivores,and soil feedback effects on the native and invasive plants and a introduced beetle feeding on them with a plant-soil feedback experiment and a lab bioassay.We also characterized fungal communities of rhizosphere of the native and invasive plant collected along a latitudinal gradient and tested their impacts on the native and invasive plants,aiming to explore the potential impacts of soil biota on north range expansion the invasive and native plants in response to climate warming.We obtained following findings:(1)The fungal and bacterial communities differed in soils that had been conditioned by the native and invasive plants in the absence of herbivores.For instance,a small proportion of fungal or bacterial OUTs were unique to soils conditioned by undamaged invasive and native plants,respectively,although these soils shared a large proportion of fungal and bacterial OTUs.For instance,pathogens Dactylaria,Exserohilum,Protomyces,Cylindrocarpon and Ralstonia were only detected in soils conditioned by undamaged invasive plants;some shared fungal,including pathogens Mycocentrospora,Phoma,Cochliobolus and Leptosphaeria and the AM fungus Entrophospora,were more abundant in soils conditioned by undamaged invasive plants.(2)Foliar herbivory by the native beetle increased the richness and diversity of mutualist fungi(including EcM and AM fungi)and herbivory altered the composition of pathogenic fungal and overall bacterial communities.Foliar herbivory altered the occurrence and relative abundance of of some fungal or bacterial genera depending on the identity of the interacting plant and insect.For instance,the pathogens such as Phaeobotryosphaeria,Cephalosporium,Devriesia,Monochaetia and the EcM fungi Tomentella were only detected in soils conditioned by defoliated plants.Herbivory also increased the relative abundance of 33 shared fungal genera and decreased the relative abundance of 34 shared fungal genera compared to the undamaged control depending on the identity of the interacting plant and insect.Herbivory increased the abundance of 51 bacterial genera and decreased the abundance of 59 bacterial genera depending on the identity of the interacting plant and insect.(3)In general,biota from soils conditioned by invasive plants had a more negative PSF on subsequent plants than biota from soils conditioned by native plants.Moreover,compared to invasive plants,tested natives plant experienced greater negative PSFs.PSF was positively predicted by Shannon diversity of the overall fungal community for both plants and there was no difference in their slopes.The survival rate of beetle larvae.was higher when feeding on plants grown in non-sterilized soil,and the beetle experienced a positive PSF when feeding on native plants.We detected no impacts of conditioning plants,herbivory or their interactions on soil total nitrogen,carbon contents.(4)Rhizosphere fungal communities and their feedback on plant change with soil sampling latitude.The relative abundance of Basidiomycota decreases,with soil sampling latitude,and the relative abundance of Phycomycota increases with soil sampling latitude.Southern population in general suffered greater negative soil feedback than north population for both species.And the negative soil feedback effects decreased with rising sampling latitudes.In summary,our study suggest that soil biota may confer a competitive advantage for invasive plants by asymmetrically suppressing susceptible native plants.and by increasing native plant palatability to foliar insects,which could not be affected by foliar herbivory.Moreover,our results suggest that during the north range expansion process both native and invasive plant will experience less negative soil feedback,which might facilitate their north range expansion in response to climate warming.