Ecological Effects Of The Coupling Of Ant-Lac Insect Mutualism And Host Plant

Mutualism relationships play a very important role in ecosystem services and functions.With honeydew as a link,the mutually beneficial relationship between ants and hemiptera insects is one of the classic model systems for studying the positive interactions between species.Taking honeydew as a link,the mutualism relationship between ants and Hemiptera insects is one of the classic model systems for studying positive interactions between species.The core content of this study is the mutualism relationship between ants and lac insects,in the research system of different land-use types such as lac seedling plantation,mature lac plantation and lac agroforestry in southwest mountainous areas,We explored the impacts of the bottom-up and top-down effects caused by mutualism between ant and lac insects and host plants on plant fitness and different trophic levels of arthropods in the systems,as well as their impacts on ecosystem services and material cycles.Results were as follows:(1)In lac seeding plantations,plant species richness had significant effects on the biomass of Cajanus cajan(F= 4.670,P= 0.010)and Dalbergia obtusifolia(F= 3.674,P= 0.290),but the ant-lac insect mutualism had no significant effects on them.The biomass of C.cajan was highest when the species richness was two and showed the best grow with D.balansae.D.obtusifolia had the highest biomass in a single plantation,the biomass decreased by the increasing species richness;The growth of D.balansae was affected by neither species richness nor interspecific interaction.The total biomass of community showed a single peak curve under a certain planting density.(2)Mutualism and plant species richness had different effects on the fitness of the four host plants,and there was no interaction between the two factors.The mutualism increased the total phenol content(F = 3.453,P = 0.040)and total nitrogen content(F = 4.851,P = 0.022)of the C.cajan,but significantly reduced the antioxidant capacity(F = 3.455,P = 0.037),it had no significant effect on soluble sugar,ground diameter and branch length.The plant species richness only had a significant positive effect on the ground diameter(F = 3.764,P = 0.026)and the branch length(F = 2.911,P = 0.05).Mutualism had no significant effect on the fitness traits of D.obtusifolia,while the plant species richness significantly reduced its total phenol(F = 2.697,P = 0.079),total nitrogen(F = 6.248,P = 0.003)and soluble sugar content(F = 4.375,P = 0.019).Mutualism had no significant effect on the fitness traits of D.balansae.From the analysis of structural equation model,plant species richness had significant negative impacts on soluble sugar(? =-0.381,P = 0.05)and ground diameter(? =-0.337,P = 0.014).Mutualism significantly reduced the total phenol content(F = 9.749,P = 0.001)and antioxidant capacity(F = 4.295,P =0.026)of the Ficus racemosa,and significantly increased the total nitrogen content(F = 3.290,P = 0.05),but had no significant effect on soluble content,ground diameter and branch length.(3)In lac seeding plantations,Ant abundance had a significant positive correlation with the lac mass(R = 0.739,P <0.001).Mutualism(F = 48.9,P <0.001)and plant abundance(F = 137.85,P <0.001)significantly increased the ant abundance in the plot,and the two treatments also had a significant impact on ant abundance(mutualism : F = 16.455,P <0.001;plant richness: F =7.396,P = 0.001).(4)Mutualism between ants and lac insects and the plant species richness had joint effects on each trophic levels of arthropod.Mutualism significantly reduced consumer abundance(F =31.916,P <0.001),and plant species richness significantly increased the consumer abundance(F= 51.560,P <0.001);mutualism had no significant effects on predator abundance,while plant species richness significantly increased the abundance of predators(F = 10.976,P <0.001).(5)From the perspective of the influence path between trophic levels,mutualism relationship had a significant top-down effect on predators and consumers.The path strength of mutualism ants to predators was stronger than that of natural control treatment.Mutualism relationship had a greater impact on predators than consumers.Plant diversity had a significant bottom-up effect on consumers and predators by affecting plant biomass,and this effect was significantly reduced as the trpphic level increased.(6)In mature lac plantations,there was no significant difference in species diversity and community structure between arboreal ants and ground ants with and without lac insects.In different lac plantations,the abundance of arboreal ants was significantly different(F = 7.256,P= 0.011).Parasitoids in different plantations also had significant differences(F = 17.108,P =0.003),and this difference was mainly caused by the abundance of arboreal ants(? =-0.707,P<0.001),lac mass and host plant species had no significant effects on parasitoids.(7)In mature lac plantations,different intensity of lac producing significantly affected the nitrogen content of plants(F=6.090,P=0.036),but had no significant effect on phosphorus and potassium.The plant nitrogen content in low-intensity of lac producing plot was significantly higher than that in the high-intensity of lac producing and in non-producing plot.Different intensity of lac producing had no significant effect on the content of total nitrogen and available phosphorus in the soils,but had a significant effect on total phosphorus(F=11.649,P=0.004),total potassium(F=14.367,P=0.002)and available potassium(F=36.158,P<0.001).The contents of total phosphorus and total potassium in the soil of the high-intensity lac producing plots were significantly lower than those of the non-producing plots.(8)In lac plantation-Amomum villosum agroforests,affected by mutualism,the abundance of arthropod communities was significantly higher than that of pure A.villosum plantations(F =5.836,P = 0.024),and the mutualism significantly increased the number of normal fruits of(F= 23.482,P <0.001),reduced the number of abnormal fruits(F = 11.923,P = 0.003).Compared with p pure A.villosum plantations,lac plantation-Amomum villosum agroforests had higher crop output.Consumers only had a certain negative impact on the normal fruits,while ants and pollinators had a significant positive effect on the normal fruits,and the ability to influence was significantly higher than that of consumers.In summary,the mutualism between ants and lac insects had a couping effect with host plant,which in turn had multiple ecological effects on the fitness and productivity on plants,the relationship between the trophic levels of arthropod communities,the nutrient cycle and services of ecosystem.These studies were not only the discussion of important frontier theories of mutualism relationships,but also the technical support and decision-making basis for mountain protection and development,and had important theoretical value and practical guiding significance.