Effects On Dynamics In Arthropod Community And Population Of Transgenic Hybrid Poplar 741 With Two Insect-Resistance

Effects and mechanisms of transgenic BtCry1Ac plus API 741 poplar on insect communities were studied by field plots investigating from the view of bionomics, population ecology, and community ecology. The experimental 741 poplar varieties were high insect-resistance hybrid poplar 741 (PB11, PB29), and medium insect-resistance hybrid poplar 741(PB17, PB1). The purpose of this study is to accumulating scientific basis for the evaluation of bio-safety of transgenic 741 poplar, utilizing the transgenic poplar reasonably. The results are as follows:1. The dominant group compositions of arthropod guilds were almost the same between transgenic 741 poplar and their control. The diversity and evenness of arthropod communities in transgenic 741 poplar were higher than the control. Density of the target pest population was significant descended, and the dominant concentration of the pest sub-community was lower significantly in contrast of the control. The dominance distribution of parasitoid enemies in transgenic 741 poplar were decended in contrast of control, the number and speciecs of the predator enemies were not significant different from those of control. So the arthropod community of transgenic 741 poplar were stable, they had better buffering action to the changing from population inside or the changing outside.2. Transgenic 741 poplar show magnificent control on dominant target pest (Lymantria dispar and Clostera anachoreta ), but the affects on non-target pests were not clear. The difference between number of dominant predator enemies in transgenic 741 poplar and its control were not significant. The population density of one dominant predator was decreased clearly in contrast of the control, that showed a obvious affection over predator enemy populations.3. Six life tables of Lymantria dispar and Clostera anachoreta were established which were fed with 2 kinds of transgenic 741 poplar and the control. The result showed that the indexes of population trend of the pest in transgenic poplar were 5.65-19.26 times lower than the control, that's means transgenic 741 poplar can reduce the density of target insect population. The highest mortality occurred at the boring stage of young instars larvae, and in transgenic poplar the mortality rate of every instars larvae were more than 90 per cent, obviously higher than the control, the most clear death factor among all were: food and environment co-affect factor, diseases and the pupa natural death caused by the transgenicpoplar.4. Predation amounts and functional responses by Cocinellas septempunctata and Misumenops tricuspidatus on Lymantria dispar which were fed with transgenic 741 poplar with BtCry1Ac and API gene, were evaluated under laboratory conditions. Both on these two preys, functional responses by the spider followed the Holling "disc equation" for type II response. When the larvae of the Lymantria dispar fed with leaves of transgenic poplar were as prey, the killed amount by the predator and the attack constant were increased and handing time were shorter than those of control. But those difference were not reach the significant level. To consider the tested results, it may be drawn that there no marked negative effect of transgenic 741 poplar on predation by Cocinellas septempunctata and Misumenops tricuspidatus.