Effect Of Foliar Insect On Soil Biota Mediated By Native Vs.invasive Plants And Its Latitudinal Pattern

In the field,non-native plant are often simultaneously affected by both above-(such as herbivores and pathogens.)and below-ground(such as pathogens and nematodes)organisms.Amounting evidence indicate that above-and below-ground biota could interact via shared hosts,and plant mediated above-and belowground interaction has become a hot issue in ecology and invasion biology in the past two decades.Previously,we have found that foliar insects,such as Agasicles hygrophila and Cassida piperata,and soil biota,such as soil microbiome and the nematode Meloidogyne incognita,could interact with each via the the invasive plant Alternanthera philoxeroides and its native congener Alternanthas sessilis.However,the mechanisms underlying plantmediated interactions between the above-and belowground organisms and how such plant-mediated interactions between the above-and belowground organisms change with latitude remain unclear.In this thesis,combining greenhouse experiment and latitudinal field survey,plant metabolome and soil microbiome analyses,I try to answer the following questions: 1)the mechanism underlying plant-mediated above-and belowground biotic interactions from the perspective of plant metabolome;2)how plant plantmediated above-and below-ground biotic interactions change with latitudes?The results indicated that: 1)Once defoliated by foliar herbivory,the component of plant leaf and root metabolome changed differently and in a species-specific manner.Once defoliated,the contents of sugar,flavonoids,polyphenols in leaves increased significantly,and the contents of indole analogues,sugar and anthocyanins in roots increased significantly for the invasive plant;the contents of indoles,phenolic amides,lipids and polyphenols while the contents of alcohols,steroids and terpenes increased in leaves,and the contents of anthocyanins,flavonols,phenolic amides and polyphenols increased but the contents of flavonoids,isoflavones and lipids decreased in the root for the native plant.2)there was a clear correlation between plant root metabolome and rhizosphere fungal and bacterial communities,and the composition of microbiome could be altered by foliar herbivory as another member in our lab had reported;3)With the increase of latitude,the diversity of plant community and soil fungal community decreased significantly.There was a significant positive correlation between the feeding intensity of herbivores and the richness of underground fungal community,but there was no significant latitudinal pattern.;4)Plant defense to root knot nematode decreased with rising latitude for the native plant,but such pattern was not evident for the invasive plant.Plant defense to herbivores increased with rising latitude for the native plant,but such pattern was not evident for the invasive plant.In addition,there was no significant correlation between herbivores resistance and nematode resistance in both invasive and native plants.These findings suggest the role of plant root metabolome in shaping foliar insect and soil biota interactions.The plant-mediated above-and below-ground interactions changed with latitude,which might in turn impose selection on plant defense.These findings improved our understanding on plant invasions from the perspective of above-and belowground interactions.