| Rice is the main and widely planted crops in China. The rice production is closely related to the arthropod trophic relationships in the rice ecosystem. Brown planthoppers Nilaparvata lugens (Stal), the most important pest of rice, has been threatening the production of rice and bringing out the series loss of agricultural economy.The aim of this study were to determine the different characteristics of the stable isotopes ratio in the arthropod samples collected in Fuyang by using C and N stable isotope analysis, and the analysis of variance of general linear model and multivariate analysis in the DPS software were utilized to reveal the different characteristics of stable isotope ratios C and N varied from different species, the arthropod trophic relationships in rice ecosystem and the primary carbon resource of rice plants for the arthropod food web; Finally, the concentrations of seven heavy metals in both N. lugens and rice plants samples collected from18different sites in southern China were measured by ICP-MS, and to calculate the elements bioconcentration factors(BCFs) by N. lugens. Cluster analysis and factor analysis for BCFs of seven elements in N. lugens were carried out to identify the bioaccumulation characteristics of heavy metals in N. lugens. The study should provide a basis for future research on the arthropod food web in rice ecosystem and the bio-accumulation characteristics as an indicator of the geographical origin for N. lugens in China. The main results of our study were as followed:1. C and N stable isotope ratios of rice plants and19arthropod species in rice ecosystem collected in Fuyang were determined by isotope ratio mass spectrometer (IRMS). C and N stable isotope ratios of different species were significantly different by the analysis of variance of general linear model. C and N stable isotope ratios in arthopod ranged from30.03‰to-26.31‰and2.10‰to6.88‰, respectively. Compared to the C and N stable ratios of rice arthropod in Korea, the conrresponding date in China were lower.2. The C and N stable isotope ratio data of19arthropod species were analyzed by principal component analysis to reveal the arthropod trophic relationships. The results showed that the C and N stable isotope of predators can be classified into two groups according to their body size, One group of smaller size includes Cyrtorrhinus livdipennis, Ummeliata insecticeps, Gnathonarium gibberum, Erigondium graminicolum, Theridion octomaculatum and Dyschiriognatha quadrimaculata; The other group consists of Paederus fuscipes, Tetragnatha maxillosa, Tetragnatha nitens, Xysticus ephippiatus, Misumenops tricuspidatsu, Argiope bruennichi, Pirata subpiraticus and Pardosa pseudoannulata. Small predators prefer to prey on small rice pests. N. lugens, Sogatella furcifera and Nephotettix bipunctatus were closely preyed by Cyrtorrhinus livdipennis, then by Theridion octomaculatum and Erigonidae spp.. Oxya chinensis were most hunted by bigger spiders, especially Pirata subpiraticus. Tetragnatha maxillosa, Tetragnatha nitens prefer to prey on lepidopterans. The enrichment of C stable isotope ratio from rice plants and rice pests revealed that rice is the main primary carbon resource in our study, but Oxya chinensis and Nephotettix bipunctatus have other carbon resouces.3. The concentrations of seven heavy metals in N. lugens and rice plants samples collected from18different sites in southern China were determined by ICP-MS to calculate their BCFs. Their BCFs showed that Zn and Mo were significantly accumulated by N. lugens in China. The cluster analysis and factor analysis for BCFs demonstrated that the bioaccumulation characteristics of seven elements in N. lugens could be classified into two groups, closely related to their molar mass. The first group is of relatively light molar masses:Cu, Zn, As and Mo, and Synergy between Cu and Zn may facilitate the bioaccumulation process; the second group included two elements with relatively heavy molar masses:Cd and Pb. These elements exhibited mutual antagonism during bioaccumulation.The study revealed that C and N stable isotope composition characteristics of different arthropod species, arthropod trophic relationships in rice ecosystem in China by using stable isotope analysis, and preliminary study on the common bioaccumulation characteristics of heavy metals by N. lugens in China. In a word, the study should provide significant reference for future study on the arthropod food web in China using of stable isotope analysis, the bioaccumulation mechanism for heavy metals in N. lugens and the bio-accumulation characteristics as an indcator for the geographical origin of N. lugens. |
