Trade-offs in the host selection by phloeophagous parasitic insects on conifers

昆虫和植物已经共存了数亿年，经常进化出密切的联系，甚至相互依存。植物和昆虫之间最常见的相互作用涉及昆虫利用植物组织作为食物和/或繁殖资源，这往往使昆虫与人类的利益直接冲突。为了应对昆虫在树林中取食或繁殖所施加的选择压力，大多数木本植物进化出了一种有效的防御性化学物质的鸡尾酒。大多数种类的昆虫只能有限地接触这些化学物质，因此只能在死亡的宿主中觅食和繁殖，但少数物种可以利用活组织，要么在宿主即将死亡时入侵它，杀死它，要么在少数情况下作为寄生虫生活。寄生昆虫对了解昆虫在选择宿主时使用的线索很感兴趣，这一点我们仍然不是很清楚。 寄主树抵御攻击的能力取决于它的活力和所使用的防御性化学物质。如果树木的活力受到损害，例如在干旱期间，树木的防御能力也会减弱，无论树木在化学上得到了多么好的保护。由于昆虫幼虫不能离开不适合的宿主，它们的母亲的错误最终会导致繁殖能力低下。保护不力的树木往往会受到许多不同昆虫的攻击，导致激烈的竞争。因此，为寄主定向的昆虫必须做出一连串的决定，涉及应对寄主防御或竞争之间的权衡。如何做出这些选择是我研究计划的重点。 将对寄生在针叶树上的两种韧皮部取食物种进行研究。使用以场为中心的方法，包括谐波雷达跟踪昆虫和化学分析来确定潜在的寄主抗性因素，我将研究昆虫使用什么线索，它们如何对它们做出反应，以做出最佳的寄主选择。这些结果将提供更多关于昆虫-植物相互作用的知识，包括了解哪些因素对针叶树的抗性起作用。

Insects and plants have co-existed for hundreds of millions of years, often evolving close associations and even co-dependence. The most common interaction between plants and insects involve the utilization of plant tissue as a food and/or breeding resource by insects, often placing insects in direct conflict with human interests. In response to the selective pressures exerted by insects feeding or breeding in wood, most woody plants have evolved a potent cocktail of defensive chemicals. Most species of insects can tolerate only limited exposure to such chemicals, and hence feed and breed only in dead hosts, but a limited number of species can utilize live tissue, either invading it as the host is dying, killing it, or in a few cases living as a parasite. The parasitic insects are of interest in understanding the cues that insects use in selecting a host, something we still don't understand very well. The ability of a host tree to defend itself against attack depends on both its vigour and the defensive chemicals used. If tree vigour is compromised, e.g., during droughts, the defensive ability of the tree will also be diminished, regardless of how well defended the tree is chemically. Since insect larvae cannot leave an unsuitable host, a mistake by their mother will ultimately result in low reproductive fitness. Poorly defended trees tend to get attacked by many different insects, leading to severe competition. Thus, an insect orienting a host must make a cascade of decisions, involving trade-offs between coping with host defense or competition. How these choices are made is the focus of my research program. Research will be conducted on two phloem feeding species that are parasitic on conifers. Using field-centred methods, including harmonic radar to track insects and chemical analyses to determine potential host resistance factors, I will examine what cues the insects use, how they respond to them to make an optimal host choice. The results will provide expanded knowledge of insect-plant interactions, including an understanding of what factors contribute to resistance in conifers.