Investigating symbiont impacts on natural enemy susceptibility in ladybird beetles.

背景资料：许多昆虫携带可遗传的共生体，即从父母传给后代的细菌，这些在瓢虫中特别常见。过去对瓢虫共生体的研究强调了生殖寄生虫的表型，如雄性杀死，但它们也可能是防御天敌攻击（保护性共生）的重要组成部分。在这里，共生体将代表一个重要的决定因素，个人的电阻和宿主-寄生虫相互作用的动态。反过来，共生体的动力学将部分由寄生虫驱动。线虫对宿主生育力的影响也使其成为使用瓢虫作为绿蝇控制措施的重要考虑因素。我们将研究寄主范围，多样性，环境和景观相关的瓢虫与tylnechid线虫寄生。目的2：我们将进行实验以分析螺原体细菌是否能在不同种类的瓢虫中提供抵抗线虫攻击的防御能力。目的3：我们将确定共生体的存在和攻击强度是否在物种内、在空间上以及在物种之间都有相关性。新奇：我们将应用最先进的下一代测序方法，调查线虫的多样性与公民科学收集和记录程序，以建立线虫在英国瓢虫物种的存在。与共生体的接口代表了新的研究，而瓢虫是一个模型系统的天敌攻击和共生体，共生体对敌人的攻击的影响还没有被确定。Timeling：尽管被发现超过50年前，线虫攻击瓢虫的多样性和强度是未知的，保存在入侵物种异色瓢虫，其中攻击率最近被证明是高的。最近对果蝇的研究表明，瓢虫体内也存在螺原体共生体，它们是一种主要的防御手段。

Background: Many insects carry heritable symbionts, bacteria that pass from parent to offspring, and these are particularly common in ladybird beetles. Past work on ladybird symbionts has emphasised reproductive parasite phenotypes such as male-killing, but it is likely that they are also an important component of defence against natural enemy attack (protective symbiosis). Here, symbionts would represent an important determinant of individual resistance and in the dynamics of the host-parasite interaction. Reciprocally, the symbiont dynamics would be driven partly by the parasite. The impact of nematodes on host fertility additionally make this an important consideration in use of ladybirds as greenfly control measures.Objective 1. We will examine the host range, diversity, environmental and landscape correlates of parasitisation of ladybirds with tylnechid nematodes. This will involve a combination of field sampling, citizen science and development of molecular ecology methods for detecting their presence and diversity.Objective 2: We will perform experiments to analyse if Spiroplasma bacteria provide defence against nematode attack in different species of ladybird.Objective 3: We will determine if presence of symbionts and intensity of attack are correlated both within species over space, and between species.Novelty: We will apply state of the art next generation sequencing methods to investigate nematode diversity with a citizen science collection and recording programme to establish nematode presence across UK ladybird species. The interface with symbionts represents novel research whilst ladybirds are a model system for natural enemy attack and for symbionts, the impact of symbionts on enemy attack has not been ascertained.Timeliness: Despite being discovered over fifty years ago, the diversity and intensity of nematode attack in ladybirds is unknown, save in the invasive species Harmonia axyridis, where attack rates have recently been shown to be high. Very recent work in Drosophila has demonstrated Spiroplasma symbionts also found in ladybirds as a principle means of defence.