Parasitoid host location: using volatiles on different spatial scales and in context of distorting elements

寄生蜂攻击广泛的昆虫，包括经济上重要的害虫物种。它们可以显著降低食草动物的密度，因此是重要的生物控制剂，但它们控制昆虫种群的有效性在很大程度上取决于它们的觅食效率。众所周知，寄生蜂利用化学信号来定位其寄主昆虫，并且在草食动物攻击后释放的草食动物诱导的植物挥发物（HIPVs）对于觅食寄生蜂具有特别重要的意义。尽管HIPV通常被认为是长距离的线索，HIPV吸引拟寄生蜂在野外条件下的距离从未被测量过，可能从不到1米到超过100米。因此，我的项目的主要目的是确定HIPVs在该领域具有吸引力的实际距离。作为一个模型系统，我将使用寄生蜂Cotesia glomerata，它攻击卷心菜白色（Pieris rafish和P. brassicae）的毛虫。要评估的距离，在该HIPVs发出的十字花科寄主植物的毛虫是活跃在该领域，我将执行标记和捕获的研究与寄生虫释放在不同的距离从毛虫侵染的植物。比较行为的寄生蜂离开释放网站和定向的运动的重新捕获的寄生蜂与HIPVs和没有将产生的信息寄生蜂的行为在有吸引力的植物挥发物的存在和不存在。这将有助于解释在不同距离的气味源释放的寄生蜂的觅食行为。HIPVs活跃的距离可能进一步受到信号强度和周围背景气味的影响。周围的非虫害的寄主植物的草食动物或不能作为寄主植物的植物物种的挥发物可能会增强寄主定位的寄生蜂，因为这些挥发物可能很容易找到，并提供有关宿主栖息地的额外信息。 同样，这些线索可能会干扰寄生蜂主机的位置提供对比信息。为了测试信号强度、身份和组成对寄生虫吸引的影响，将用不同数量的被侵染和未被侵染的植物以及非宿主植物重复田间实验。此外，控制嗅觉仪和风洞实验与不同的植物挥发物将在实验室进行。知道的空间尺度，HIPVs是在田间条件下的吸引力，以及这个距离是如何影响非主机挥发物将大大提高我们的昆虫觅食和分布的理解，并将提高基于挥发物的害虫控制策略的效率。

Parasitoid wasps attack a wide range of insects, including economically important pest species. They can drastically reduce herbivore density and are thus important biocontrol agents, but their effectiveness in controlling insect populations depends strongly on their foraging efficiency. It is well known that parasitoids use chemical cues to locate their host insects and that herbivore-induced plant volatiles (HIPVs) which are emitted after an herbivore attack are of special importance for foraging parasitoids. Even though HIPVs are often considered to act as long-range cues, the distance at which HIPVs attract parasitoids under field conditions has never been measured and may range from less than 1 m to more than 100 m. Therefore, the main aim of my project is to determine the actual distance over which HIPVs are attractive in the field.As a model system I will use the parasitoid wasp Cotesia glomerata, which attacks caterpillars of the Cabbage white (Pieris rapae and P. brassicae). To assess the distance, at which HIPVs emitted by the brassicaceous host plants of caterpillars are active in the field, I will perform mark-and-capture studies with parasitoids released in different distances from caterpillar infested plants. Comparing behavior of parasitoids that leave the release site and the directedness of movement of recaptured parasitoids with and without HIPVs will yield information about parasitoid behavior in the presence and absence of attractive plant volatiles. This will help to interpret foraging behavior of parasitoids that are released at different distances from the odor source.The distance over which HIPVs are active may further be influenced by the strength of the signal and by the surrounding background odor. Volatiles from surrounding non-infested host plants of the herbivore or from plant species that cannot be used as host plants may enhance host location by parasitoids, because these volatiles may be easy to locate and provide additional information about the host habitat. Similarly, these cues may interfere with parasitoid host location by providing contrasting information. To test the influence of signal strength, identity and composition on parasitoid attraction, the field experiment will be repeated with different numbers of infested and non-infested plants as well as non-host plants. Additionally, controlled olfactometer and wind-tunnel experiments with different plant volatiles will be performed in the laboratory.Knowing the spatial scale over which HIPVs are attractive under field conditions and how this distance is influenced by non-host volatiles will drastically improve our understanding of insect foraging and distribution and will increase the efficiency of volatile-based pest control strategies.