Cascading effects of predator and herbivore diversity and their interaction

由于担心物种灭绝可能造成的有害影响，近年来开展了大量研究工作，以确定物种灭绝对生态系统的影响。这些研究大多控制了单一营养水平的物种数量，通常是植物，并监测了生态系统功能的直接后果，例如植物生物量的产生量。这些实验是不现实的，原因有很多：在现实系统中，营养水平较高的物种（如食肉动物）更有可能灭绝；物种可能同时从多个营养水平上消失（例如，捕食和食草物种）；而且后果可能比物种消失的营养水平更深远，例如，捕食者物种的消失可能影响食草动物，而食草动物又可能影响植物。本文提出的研究将通过一项实验研究来解决这些缺陷，在实验研究中，捕食者和食草动物（捕食者的猎物）的物种数量是独立操纵的。该实验将确定捕食者物种数量的变化是否会通过食物链传播，从而影响食草动物、植物和土壤微生物的生物量。它还将测试食草动物的物种数量，或食草动物在不同寄主植物上的分布模式，是否会影响通过食物网传播的效应。该实验将揭示物种丧失对生态系统的影响以及这些影响发生的机制的新信息。这对保护生物学和农业生态系统中昆虫物种的管理具有深远的意义。

Concern over possible detrimental effects of species extinction has led to a large research effort in recent years to determine how ecosystems are affected by species loss. Most of these studies have manipulated the number of species at single trophic levels, usually plants, and monitored proximate consequences for the functioning of the ecosystem e.g. the amount of plant biomass produced. These experiments are unrealistic for a number of reasons: in real systems, species at higher trophic levels (e.g. predators) are more likely to become extinct; species are likely to be lost from multiple trophic levels at the same time (e.g. predator and herbivore species); and consequences are likely to be further reaching than the trophic level at which species are lost e.g. predator species loss may affect herbivores which may in turn affect plants. The proposed research will address these shortcomings with an experimental study in which the number of species of predator and herbivore (prey of the predators) are manipulated independently. The experiment will determine whether changes in predator species number propagate through the food chain to affect herbivore, plant and soil microbe biomass. It will also test whether herbivore species number, or the pattern of distribution of herbivores on different host plants, affects the propagation of effects through the food web. The experiment will reveal novel information about the effects of species loss on ecosystems and the mechanisms by which these effects occur. This has far reaching relevance for conservation biology and for the management of insect species in agricultural ecosystems.