Predicting the ecological impacts of invasive alien insects at multiple levels: from genes to communities

生物入侵是影响生态系统、经济以及人类、动物和植物健康的全球现象。近年来，由于全球贸易增加了生物以前所未有的速度在全球范围内运输的途径，生物入侵的发生速度呈指数级增长。因此，事先了解外来生物可能对它们所入侵的生态系统造成的影响是非常重要的。在入侵动物中，顶级捕食者尤其令人感兴趣，因为它们直接影响它们所捕食的广泛生物，并间接通过释放敌人等方式产生影响。在这个博士项目中，学生将采用一系列实验方法，从分子方法到行为和群落分析，来表征昆虫顶级捕食者的关键特征在生物入侵后是否发生了变化，以及它们对生态系统的实际和预测影响。学生将比较分析两种引人注目的昆虫入侵者：亚洲大黄蜂Vespa velutina（最近的入侵者）和harlequin瓢虫Harmonia axyridis（建立于欧洲）。因此，这两个系统提供了一个很好的机会来比较与相对“古老”的入侵（Harmonia）和较新的入侵（Vespa）相关的关键生态特征，并增强了预测这两种昆虫可能对入侵生态系统造成的影响类型的潜力。该学生将在英国、欧洲和北美进行实地考察，对这两种昆虫进行取样，这些昆虫来自不同的种群，代表了它们入侵历史上的一个梯度，他们将在实验室进行实验，测试可能与成功入侵有关的行为和生理特征。两个特征将被优先考虑：摄食行为/生态和免疫能力。捕食分析将结合密度依赖的猎物消耗和偏好模式，稳定同位素分析和DNA元条形码，在更大范围内表征两种昆虫的饮食组成，并采用高通量宏基因组方法以最高分辨率识别猎物。对于免疫能力，候选基因方法将用于表征与构成和诱导反应相关的关键基因的表达模式。这种实验方法将为统计分析奠定基础，以模拟Vespa和Harmonia对生态系统的影响。接下来将采用另一种建模方法来预测顶级捕食者如何随着时间的推移影响英国的生态系统。

Biological invasions are global phenomena that impact ecosystems, the economy and human, animal and plant health. The rate at which biological invasions occur has grown exponentially in recent times, due to global trade that has increased the pathways for organisms to be transported across the globe at unprecedented speed. It is therefore of high importance to understand in advance the impact that alien organisms might pose to the ecosystems that they invade. Among invasive animals, top predators are of particular interest, as they directly impact on a wide range of organisms that they prey upon, and also cascade their effects indirectly through, for example, enemy release.In this PhD project, the student will adopt a series of experimental approaches, that span from molecular methods to behavioural and community analyses, to characterize whether key traits of insect top predators have shifted after biological invasions and also their actual and predicted impacts on ecosystems. The student will comparatively analyse two high profile insect invaders: the Asian hornet Vespa velutina (a recent invader) and the harlequin ladybird Harmonia axyridis (established in Europe). Hence, the two systems present a great opportunity to compare key ecological traits associated with a relatively 'old' invasion (Harmonia) vs. a more recent one (Vespa), with an enhanced potential to predict the type of impact that these two insects might have across invaded ecosystems. The student will perform field work in the UK, Europe and North America to sample insects of the two species from different populations representing a gradient in their history of invasion, and the will perform experiments in the lab to test behavioural and physiological traits that could be associated with successful invasions. Two traits will be prioritised: feeding behaviour/ecology and immunocompetence. Feeding analyses will combine density dependent patterns of prey consumption and preference with stable isotope analyses and DNA metabarcoding, to characterize the composition of the diet of the two insects at a broader scale, and also with a high-throughput metagenomic approach to identify prey items at the highest resolution. For immunocompetence, a candidate gene approach will be used to characterize the expression patterns of key genes associated with constitutive and induced responses. This experimental approach will lay the ground for a statistical analysis to model the impact that Vespa and Harmonia are having on the ecosystem. This will be followed by another modelling approach to predict how top predators could impact UK ecosystems over time.