Using multispecies evolutionary history to test hypotheses of community assembly

世界上的生物多样性由复杂的动物(特别是昆虫)和植物群落主导。尽管我们知道这些群落是如何运作的(例如，谁吃谁)，但我们对它们是如何形成的知之甚少：它们是由相互作用了数百万年的物种组成的，还是由最近才从不同来源聚集在一起的一组物种组成的？对于我们解释捕食者和猎物适应的方式来说，以下哪一项是重要的。长时间的联想意味着捕食者和猎物可能已经进化出了对彼此非常特定的反应--以一种通常被称为“军备竞赛”的进化形式。相比之下，如果群落是最近才建立起来的，组成物种的生物学不太可能由其他群落成员塑造。这些中的哪一种是正确的，在保护方面也可能是重要的：如果物种有很长的进化历史，那么它们分享的互动(例如捕食者吃猎物，或者传粉者与植物的关系)也是古老的、特殊的，应该被保存下来。相比之下，如果群落通常是在短时间内(按照进化时间表)从可用的物种集合中聚集起来的，那么它表明群落的相互作用也可以相对快速地进化，并且群落在进化上是年轻的。如果社区是年轻的，这也意味着它们很容易受到新物种的入侵--需要对人类有意(如生物控制剂)或无意引入的物种进行仔细管理。在这个项目中，我们将计算出对于一个特定的群落来说，这些情景中的哪一种更真实--栖息在橡树和其他植物上的昆虫。这些群落很容易研究，并且在许多重要方面与其他昆虫植物群落相媲美。我们将使用DNA序列来找出胆汁群落中不同类型的捕食者和猎物起源于哪里，然后传播到世界各地。如果群落中的物种有很长的共同历史，那么我们预计每个物种都会起源于相同的地方，以相同的方式传播。相比之下，如果捕食者在进化过程中在一定范围内抓住了猎物，那么我们预计不同的群落成员会有不同的起源和范围扩大的模式。我们将从两个层面来考虑这个问题--全球(横跨北美、亚洲和欧洲)和区域(包括欧洲和小亚细亚的西部古北区)。我们项目的一个重要组成部分是评估欧洲以东地区(特别是土耳其)对欧洲保护的重要性。许多‘欧洲’物种(如‘英格兰橡树’和家鼠)在欧洲东部很远的地方被发现，但东部地区的保护价值通常不被考虑。我们正在研究的橡树巨蜂系统的初步信息表明，在扩散到欧洲之前，橡树和巨蜂在那里都是多样化的。我们将观察橡树胆中的捕食者，看看这种来自东部的模式是否真的适用于整个社区。

The world's biodiversity is dominated by complex communities of animals (particularly insects) and plants. Though we know something of how these communities function (for example, who eats whom), we know very little about how they come to be: do they consist of species that have interacted for millions of years, or do they consist instead of sets of species that have only very recently come together from different sources? Which of these is true is important for the way in which we interpret adaptations in predators and prey. Long associations mean that predators and prey may have evolved very specific responses to each other - in a form of evolution commonly termed an 'arms race'. In contrast, if communities are only recently put together, the biology of component species is unlikely to have been shaped by the other community members. Which of these is true is also likely to be important in conservation: if species share a long evolutionary history, then the interactions they share (such as a predator eating its prey, or a pollinator's relationship with a plant) are also ancient, special, and should be preserved. In contrast, if communities are commonly assembled over short periods (on an evolutionary timescale) from available sets of species, then it shows that community interactions can also evolve relatively quickly, and that communities are evolutionarily young. If communities are young, it also means that they are vulnerable to invasion by new species - requiring careful management of species that humankind introduces either intentionally (as in biocontrol agents) or unintentionally. In this project, we will work out which of these scenarios is more true for one particular community - the insects inhabiting galls on oaks and other plants. These communities are easy to study, and match in many important respects other insect-plant communities. We will use DNA sequences to work out where different types of predators and prey in the gall communities originated and then spread around the world. If species in communities have a long shared history, then we expect each species to originate in the same place and spread in the same way. In contrast, if predators have 'latched on' to their prey at a range of points through evolutionary time, then we expect different community members to have different origins and patterns of range expansion. We will look at the question at two levels - globally (across North America, Asia and Europe), and regionally (for the Western palaearctic, which includes Europe and Asia Minor). An important component of our project is assessing the importance of regions just east of Europe (particularly Turkey) for European conservation. Many 'European' species (such as the 'English oak', and house mouse) are found far to the east of Europe, but the conservation value of eastern regions is not usually considered. Initial information for the oak gallwasp system we are studying suggests that oaks and gallwasps both diversified there before spreading into Europe. We will look at the predators in oak galls to see if this 'out of the east' pattern is in fact true for the whole community.