Regulation of Underground Insect Herbivores: Subterranean Trophic Cascades?

本研究的重点是一个地下营养级联，涉及一种食根蛾毛虫、一种灌木羽扇豆、一种土栖昆虫病原线虫以及该线虫的捕食者。正是线虫捕食者引发了这一连锁反应。这些捕食者主要是噬线虫真菌，它们是物种，在土壤中丰富。营养相互作用的结构如下：被毛虫杀死的羽扇豆的尸体是蘑菇的底物，蘑菇被认为是噬线虫的生殖阶段。具有相反的潜在效应，含有丰富的生物碱的叶子是有效的杀菌剂，在真菌噬线虫阶段的土壤栖息地上积累成厚厚的毯子。毛毛虫和线虫似乎都没有受到这些生物碱的影响，它们只消耗生物碱含量低的木材。毛虫广泛分布在羽扇豆斑块中，但其数量与线虫丰度呈负相关。线虫经常遭受局部灭绝，只存在于羽扇豆属植物繁茂的地区。然而，在毛虫密度高的地方，羽扇豆凋落物和以线虫为食的真菌都很丰富。在这些地方，有一些线虫。土壤是地球上最鲜为人知的生命栖息地之一。地下昆虫食草动物种类繁多，对植物有害，对生态系统有影响，在农业系统中已经得到了一定程度的研究，但生态学家只对其进行了粗略的研究。地下食草昆虫的种群调控一直被农学家和生态学家所忽视。地下昆虫来自我们熟悉的地上昆虫群，但它们在土壤中的天敌却与众不同。这项研究与了解自然和农业群落中调节地下食草动物种群的因素有明确的联系。

9508673 STRONG This research focuses on a below-ground trophic cascade involving a root-feeding moth caterpillar, a bush lupine, a soil-dwelling entomopathogenic nematode, and predators on this nematode. It is the nematode predators that initiate this cascade. These predators are primarily the nematophagous fungi impertecti, which are speciose and abundant in soils. The trophic interactions are constructed as follows: Dead lupine killed by caterpillars are substrates for mushrooms that are putatively the reproductive stages of the nematophages. With opposite potential effect, leaves bearing copious alkaloids that are potent fungicides accumulate in thick blankets on the soil habitat of the nematophagous stages of the fungi. Neither the caterpillar, which consumes only wood low in alkaloid, nor the nematode appear to be affected by these alkaloids. The caterpillars are widely dispersed among lupine patches, yet their numbers are negatively correlated with nematode abundance. The nematodes suffer frequent local extinctions and are present only in areas where lupines flourish. However, where caterpillar densities are high, both lupine litter and the nematode-eating fungi are abundant. In these areas, there are a few nematodes. Soils are among the most poorly known habitats of life on earth. Underground insect herbivores, which are diverse, injurious to plants, and influential in ecosystems, have been studied to a degree in agriculture systems, but have had only had cursory treatment by ecologists. Population regulation of underground insect herbivores has been almost totally ignored by agriculturalists and ecologists alike. While underground insects are drawn from familiar above-ground groups, their natural enemies in the soil are distinctive. This research has clear linkages to understanding factors that regulate populations of below-ground herbivores in natural and agricultural communities.