转Bt基因棉田节肢动物群落营养层及优势功能团的组成与变化

Structure and Seasonal Dynamics of Arthropods in Transgenic Bt Cotton Field

1 998年在河北南皮棉区转 Bt基因棉棉田和常规棉综防田的生物群落变化的研究表明 :与常规棉综防田相比 ,转 Bt基因棉棉田的节肢动物种类增加 30 .7% ,功能团多样性增加 6 6 .9% ,天敌类和中性节肢动物类的丰富度分别增加97.6 %和 1 5 8.0 % ,害虫类的丰富度减少 4 5 .7%。就功能团的种群数量来看 ,主要害虫棉铃虫、蚜虫和蓟马种群数量分别减少 98.9%、6 9.0 %和 72 .6 % ;而次要害虫害蝽、粉虱、叶蝉类昆虫的种群数量分别增加了 2 .2、3.2和 1 4 .8倍。棉花生长中期 ,转 Bt基因棉棉田中的基位物种丰富度大于中位和顶位物种 ;常规棉田中的差异则更大 ,出现天敌控制“空缺”。综合分析表明 ,转 Bt基因棉棉田生态系统比常规棉综防田稳定 ;转 Bt基因棉棉田的中性节肢动物和次要害虫在害虫 -天敌的营养链中起到了重要的调控作用。

To understand the ecological impacts of the transgenic Bt (CryI(c)) cotton on natural enemies of the target pest, Helicoverpa armigera (Hübner), and non-target arthropods in cotton fields, a systematic survey was made in a transgenic (Bt) and a conventional cotton field in Nanpi county, Hebei Province in 1997. Both plots were about 0.3 hm 2. All arthropod species and their numbers were recorded by visual observation on 100 plants in 10 standard sampling spots between May and October at five-day intervals. The non-target insect pests, natural enemies and neutral arthropods were distinguished, based on their trophic relationships, as well as taxonomy. Species richness, species abundance and community diversity indices were used to analyze and compare the seasonal trends of different functional groups in both cotton fields. The systematic survey showed that: (1) More species and individuals were observed in the Bt-cotton plot than the conventional plot. The number of phytophagous species was 43 in Bt-vs. 28 in conventional plot, there were 56 (Bt-) vs. 46 (conventional) natural enemy species. Sixteen species in Bt-cotton and 14 species in conventional cotton were classified as ‘neutral'. (2) The individual numbers for the categories of pests, natural enemies and neutral arthropods were 12941, 8690 and 10790, respectively, in transgenic Bt cotton field; while 15616, 2880 and 2739 in the conventional plot. Thus, the average abundance of natural enemies and neutral arthropods in transgenic Bt cotton field increased by 97.6% and 158.0%, respectively, whereas the abundance of phytophagous pests decreased by 45.7%. (3) In transgenic Bt cotton field, the populations of cotton bollworm (H. armigera), decreased by 98.9% compared to the conventional plot; the aphid Aphis gossypii and the thrip (Heliothrips indicus Bagnall), decreased by 69.0% and 72.6%, respectively. The phytophagous bugs (Lygus lucorum and Adelphocoris rapidus), cotton whitefly (Bemisia tabaci Gennadius) and leafhopper (Empoasca biguttula) increased by 2.2, 3.2 and 14.8 times, respectively. The abundance of natural enemy and neutral insect group in both fields were significantly higher than that of insect pest group at the early and late cotton growing seasons, but much lower at the middle growing season. The ratio of insect pest to natural enemy in the middle cotton growing season was 1.68 : 1 in transgenic Bt cotton field, and 6.78∶1 in the conventional IPM cotton field. Compared to the conventional IPM cotton field, the species diversity and functional groups diversity in transgenic Bt cotton field decreased by 15.3% and 66.9%, respectively. Biodiversity and functional groups abundance dynamics indicated that the arthropod community in transgenic Bt cotton field was more stable than that in the conventional IPM cotton field. The neutral arthropods and secondary pests played an important role in regulating food chain of pest-natural enemy.