Tahvanainen Jorma O, Root Richard B
Department of Entomology, Cornell University, 14850, Ithaca, New York, U.S.A.
Oecologia. 1972 Dec;10(4):321-346. doi: 10.1007/BF00345736.
The population ecology of Phyllotreta cruciferae Goeze, a flea beetle which is an important pest of cole crops (Brassica oleracea) in central New York was studied in experimental gardens of differing vegetational diversity over a three year period. Adult beetles were more abundant on collards (B. oleracea var. acephala) grown in monocultures than on those grown adjacent to natural vegetation. The emergence of individuals forming the new annual generation was also greater in the pure stands. Predators and parasites appeared to have a negligible influence on the adult beetles in both habitats. Further experiments demonstrated that monocultures were colonized more rapidly and experienced greater feeding damage than stands in which collards had been interplanted with tomatoes and tobacco. Choice experiments in the laboratory showed that chemical stimuli given off by non-host plants (tomato, Lycopersicon esculentum, and ragweed, Ambrosia artemisiifolia) interfered with the host finding and feeding behaviour of P. cruciferae. These results indicate that vegetational diversity can exert a direct influence on populations of phytophagous insects.We conclude that the environmental capacity (Determination in Schwerdtfeger's terminology) of diverse natural communities is lower than that of natural or man-made monocultures. The "associational resistance" resulting from the higher taxonomic and microclimatic complexity of natural vegetation tends to reduce outbreaks of herbivores in diverse communities.
在纽约州中部，对十字花科跳甲（Phyllotreta cruciferae Goeze）的种群生态学进行了为期三年的研究，该跳甲是甘蓝作物（Brassica oleracea）的一种重要害虫。在不同植被多样性的实验园中进行研究。与种植在自然植被旁边的羽衣甘蓝相比，单作种植的羽衣甘蓝（B. oleracea var. acephala）上的成年甲虫数量更多。在纯种田中，形成新一年代的个体的羽化率也更高。在这两种生境中，捕食者和寄生虫对成年甲虫的影响似乎可以忽略不计。进一步的实验表明，与羽衣甘蓝与番茄和烟草间作的田块相比，单作田块被定殖的速度更快，遭受的取食损害更大。实验室中的选择实验表明，非寄主植物（番茄，Lycopersicon esculentum，和豚草，Ambrosia artemisiifolia）释放的化学刺激会干扰十字花科跳甲的寄主寻找和取食行为。这些结果表明，植被多样性可以对植食性昆虫的种群产生直接影响。我们得出结论，多样化自然群落的环境容量（用施韦特费格的术语表示为“测定值”）低于自然或人工单作群落。自然植被较高的分类学和小气候复杂性所产生的“联合抗性”往往会减少多样化群落中食草动物的爆发。
