农业景观结构对麦蚜寄生蜂群落组成的影响

Community composition of parasitoids and hyperparasitoids of wheat aphids in different agricultural landscapes

麦蚜是中国北方小麦上最重要的害虫之一,既能直接刺吸危害也可传播多种病毒,但麦蚜通常的危害期只有2～3个月。随着现代农业与设施农业的发展,农业景观结构发生了巨大的改变,整个麦蚜寄生蜂群落也随之发生了显著的变化。经典假说认为复杂的农业景观能够维持局部的物种多样性及种间关系,也能够维持更大的天敌资源。作者在4种不同的麦田景观类型下研究了麦蚜及寄生蜂的群落结构,发现简单农业景观与复杂农业景观中寄生蜂寄生率与多样性差异不显著,但初寄生蜂在800m2左右的生境面积中寄生率与多样性最高,重寄生蜂却并没有表现出这种分布,而在更大的生境中重寄生率与多样性更高。研究结果表明:1)生境面积是影响麦蚜及寄生蜂群落的重要因子,2)简单农业景观与复杂农业景观下麦蚜及寄生蜂群落多样性差异不显著,3)一定程度的生境破碎化能够促进初寄生蜂的种群而抑制重寄生蜂的种群,但高度的生境破碎化会同时抑制2种寄生蜂的种群。

Wheat aphids are the most serious pests of wheat crops in northwest China, causing damage either directly by feeding on wheat plants, or by transmitting viruses to wheat plants. These pests are present for 2—3 months each year in wheat fields. The community of aphids and their parasitoids and hyperparasitoids has experienced considerable change due to the modernization of agriculture. One hypothesis suggests that structurally complex landscapes may enhance local species richness and interactions, possibly because they support a higher species pool. This hypothesis was tested on wheat aphids, parasitoids and hyperparasitoids by comparing 4 different spring wheat landscape types. Surprisingly we found no difference in species richness between simple and complex landscapes. Although the diversity and numbers of parasitoids was highest in habitats of moderate size, there was no significant difference in the diversity of hyperparasitoids in the different landscape types. We conclude that habitat area was an important factor influencing parasitoids in wheat fields, with habitats of moderate size harboring abundant parasitoids and high species diversity. We also conclude that landscape complexity has no effect on the diversity of parasitoids and hyperparasitoids. Finally we conclude that habitat fragmentation can, to some extent, help parasitoids suppress hyperparasitoids.