Host shifts and host-associated differentiation in herbivorous insects: ecological causes and consequences

地球上生命最明显的特征之一是其惊人的多样性-至少有100万种是科学已知的，也许还有多达3000万种有待发现。 然而，有些谱系比其他谱系更加多样化，而解释这种差异性成功是进化生态学中最基本的问题之一。 “高度多样性”最引人注目的例子是以植物为食的昆虫和攻击它们的拟寄生虫--多达一半的动物物种可能属于其中的一个群体。 植食性昆虫和拟寄生物进化成功的一个原因可能是它们倾向于进化出专门的饮食。 饮食通过宿主转移（向饮食中添加新的宿主植物）进化，然后通过宿主相关分化（HAD）进化新的多样性，其中单个饮食通才分化形成一对新的宿主专业物种。 虽然宿主转移和HAD是常见的，但它们并不普遍，不同的谱系可以在不同的时间和速率以及通过不同的机制经历这些过程。 我的研究计划旨在了解控制主机转移和HAD发生的生态因素，通过研究以两种常见的加拿大一枝黄花为食的各种昆虫。 通过比较生态学和种群遗传学的物种是进化成对的主机专家，与那些继续喂养作为通才，我们可以测试假设的力量，有利于或阻碍多样化。 我们目前的重点是昆虫的寄主植物个体之间的性状变异的偏好，可以驱动他们的进化反应，寄主植物物种之间的变化。 对宿主转移和HAD的预测性理解将有助于我们了解地球生物多样性的起源，以及预测和管理昆虫对农业和农林系统中新宿主的攻击。 我们还将通过测试草食动物对其宿主植物的影响随着进化时间的推移而减少的假设来建立我们的HAD工作，因为植物进化出更大的耐受性，昆虫的毒性降低。 如果这是真的，由宿主转移和HAD产生的新的昆虫-草食动物协会应该表现出比古代更高的影响。 这一点很重要，因为这种新的昆虫-草食动物协会也是入侵物种传播的结果，在全世界造成了巨大的和不断增加的生态和经济成本。

One of the most obvious features of life on Earth is its astonishing diversity - at least a million species are known to science, and perhaps as many as 30 million more remain to be discovered. Some lineages have diversified much more abundantly than others, though, and accounting for this differential success is one of the most fundamental questions in evolutionary ecology. Among the most spectacular examples of "hyperdiversity" are plant-feeding insects and the parasitoids that attack them - as many as half of all animal species may belong to one or the other of these groups. One reason for the evolutionary success of plant-feeding insects and parasitoids may be their tendency to evolve specialized diets. Diets evolve via host-shifting (adding new host plants to diet), and then new diversity evolves by host-associated differentiation (HAD), in which a single diet generalist diverges to form a new pair of host-specialist species.      While host-shifting and HAD are common, they are not universal, and different lineages can undergo these processes at different times and rates and by different mechanisms. My research program seeks to understand the ecological factors that control the occurrence of host-shifting and HAD, by studying the diverse set of insects feeding on two common Canadian goldenrods. By contrasting the ecology and population genetics of species that are evolving pairs of host specialists, vs. those that continue to feed as generalists, we can test hypotheses about forces that favour or retard diversification. Our current focus is on the way insect preferences for trait variation among host plant individuals can drive their evolutionary response to variation between host plant species. A predictive understanding of host-shifting and HAD will help us understand the origin of Earth's biodiversity, as well as to anticipate and manage attack by insects on novel hosts in agricultural and agroforestry systems. We will also build on our HAD work by testing the hypothesis that the impact of herbivores on their host plants lessens over evolutionary time, as the plants evolve greater tolerance and the insects reduced virulence. If this is true, novel insect-herbivore associations generated by host-shifting and HAD should show higher impact than ancient ones. This is important, because such novel insect-herbivore associations also result from the spread of invasive species and have enormous and increasing ecological and economic costs worldwide.