Effects Of Ageratina Adenophora Invasion On The Structure Of Native Plant Leafspot Fungal Pathogens

Biological invasion is a global ecological phenomenon and,for a long time,has been caused harm not only to the biodiversity but also to the global ecological environment and economic development worldwide.Invasive plants are the most aggressive species in biological invasion and endanger greatly the local ecosystem,agriculture,forestry and animal husbandry and so on.However,previous concerns about the harm of invasive plants has been mainly focused on the macroscopic and visible direct effects of plant itself on ecosystems.In recent years,research has gradually shown that in many cases,the competitiveness of invasive plants is determined by the new relationship between invasive plants and local microbes rather than by plants themselves.In China,as an invasive plant Ageratina adenophora seriously threatens the local ecological balance.It changes the local habitat through a series of competitive mechanisms,and produces a wide influence on the local species and its ecosystem.In terms of long-term and regional ecological risk,however it is rare the research on the influence of A.adenophora on the microbial community structure in the invasive ecosystem.Therefore,this experiment,by means of traditional culture and molecular biology,tries to find out whether the invasion of A.adenophora will change the population structure of the pathogen of local plant leafspot,and aims to provide a new way to explore the successful invasion mechanism of A.adenophora,as well as other invasive plants in the future.In this study,1480 leafspot fungal strains were obtained from 20 native plant species collected from 12 invaded sites and 7 noninvaded sites of A.adenophora in Yunnan Province,using traditional isolation and culture techniques.Furthermore,241 leafspot fungal pathogens were screened by field pathogenicity test from 12 native plants,including 5 species of trees: Alnus nepalensist,Betula alnoides,Cyclobalanopsis glaucoides,Quercus variabilis,and Amygdalus persica;4 species of vines: Dioscorea hemsleyi,Memorialis hirta,Cynanchum otophyllum,and Fallopia multiflora;2 sepecies of shrubs: Rubus ellipticus and Rubus parvifolius,and one economic crop Nicotiana tabacum.These pathogens are grouped into 34 species based on their ITS gene sequences.The following conclusions were obtained after analyzing the community structure of leafspot fungal pathogens in invaded and noninvaded areas.1.The community structure and quantity of leafspot fungi and pathogens in the A.adenophora invaded area and noninvaded area are significantly different.The community structure of leafspot fungi and pathogens in native plants is very different between the invaded and noninvaded areas.The fungal dominance of the invaded and noninvaded areas is mainly different in the species and abundance of numerically dominant OTUs.For example,genus Colletotrichum is the most dominant one either among the leafspot fungi or leafspot fungal pathogens.However,OTU1 is the most dominant in the invasion area but OTU10 in the non invaded region of A.adenophora;in the genus Diaporthe,the most dominant ones in the invaded area and noninvaded area were OTU6 and OTU153,respectively;in the genus Epicoccum,the most dominant ones in the invaded area and noninvaded area were OTU2 and OTU3,respectively.2.The microenvironment of different sampling sites had certain effects on the community structure and quantity composition of leafspot fungi and pathogensTotally,no difference was detected among different sampling sites in term of the species diversity index of local plant leafspot fungi and pathogens.However,there were significant differences in the community structure and quantity of the leafspot fungi and pathogens among sampling sites after non parametric multifactor analysis of variance and PCoA analysis.This may be due to the differences in physic-chemical and biological microenvironment of native plants in each sampling site.3.The community structure and quantity of leafspot fungi and pathogens showed no difference between different life-type plants in the A.adenophora invaded area,but significant differences in noninvaded area.The data of non parametric multifactor analysis of variance and PCoA analysis showed that there was no obvious difference in the structure of fungi communities of different life-type plants in the invasive region of A.adenophora,but there were obvious differences in the noninvaded area.It is assumed that in the noninvaded ecosystem,the distribution patterns of leafspot fungi and pathogens are different among different local life-type plants mainly due to the growth space isolation of host plant in the habit,both horizontally and(or)vertically.However,A.adenophora invasion occupied the empty niches originally and thus destroyed the segregation of these host plants,which returns to increase the fungal transmission in local habitats and homogenizing the fungal communities of different life-type plant hosts..In conclusion,this result shows that A.adenophora invasion has changed the community structure and quantity of leafspot fungi and pathogens in local plants,and generates potential ecological risk.