The Effect Of Transgenetic Cotton On Biodiversity Of Beetles And Decomposition Rate Of Leaf Litter

Ground beetles are an important component of biological communites in argriculture systems,and they are not trivial to biodiversity maintenance,pest control and ecosystem nutrient cycling and energy flow.Ground beetles have been shown to be sensitive to environmental disturbances,such that they can serve as an environmental indicator.Planting transgenic Bt cotton may extensively suppress herbivorous insect population and improve cotton yield.However,insecticidal Bt protein from transgenic cotton can be detrimental to environmental quality.Numerous studies have examined the effect of Transgenic Bt cotton on target and non-target insect population dynamics,but the knowledge regarding beetle diversity and associated ecosystem functions is lacking.In the passing years,I first investigated how ground beetle diversity and species composition respond to environmental disturbances in natural ecosystems,and then I examined the responses in agricultural systems around Wuhan,Yancheng,and Nanjing cities.I also experimentally recorded the diet preference of the dominant and sensitive beetle species,Chlaenius bioculatus.Furthermore,I invesigated the decomposition rate of transgenetic and non-transgenetic cotton leaves at a Nanjing farmland.The main results are shown as follows.(1)In the natural ecosystem,species diversity and composition of the ground beetle community were sensitive to environmental disturbances.Both species richness and species diversity of ground insects and beetle increased with increasing disturbance levels,especially for large predatory beetles.(2)In the farmland ecosystems,both species richness and species diversity of ground insects and beetles were higher in non-transgenetic than in transgenetic cotton field.C.bioculatus was found to be the most dominat species among predtoary beetles and its abundance was lower in transgenetic cotton field.(3)C.bioculatus preferred cotton bollworm as food sources to other potentials including Anophia leucomelas,earthworm,Brachmia macroscopa,Acrida cinerea,Oxya chinensis and Tarbinskiellus portentosus.In a field survey,we observed that C.bioculatus climbed on cotton plant crowns to prey on bollworms.Therefore,C.bioculatu can be used as an indicator species to monitor environmental change due to transgenetic cotton plantation.(4)In both abandoned field and cotton plantation,the decomposition rate of non-transgenic cotton leaf litter was higher than that of transgenic cotton.In conclusion,my study demonstrates that planting trans-genetic Bt cotton tends to reduce beetle biodiversity and richness,and in particular decrease large predatory beetle abundance.In addition,planting trans-genetic cotton tends to decrease leaf decomposition rates and damp nutrient cycling of aricutural ecosystems.