Developing novel molecular tools for characterising food web responses to climate change

该项目的目的是量化全球变暖对淡水生态系统食物网结构的影响。我将研究这些链接的强度，以及几种不同食物网在温度梯度上的能量流动方向。为了解决这些关键的生态问题，我将测试新的分子技术，如下一代测序（NGS），它将与更传统的食物网方法相匹配。特别是，通过对物种的部分遗传密码进行测序，并将其与数据库进行比较，而无需参考其形态特征，就可以识别物种。事实上，这些技术的使用为我们提供了极有价值的信息：我们可以检测到形态相同但具有不同遗传特征的隐种(I)的存在，还可以识别在此阶段无法区分的早期幼虫（II），但它在损坏标本（III）方面也很有用。此外，我将利用西尔伍德公园的新生态环境设施来预测变暖对淡水生态系统稳定性和结构的影响，特别是我们的目标是将生态环境加热4摄氏度和7摄氏度，这是我们预计在下个世纪在我们的纬度和高纬度地区分别遇到的温度。在多塞特（英国）进行的一项长期中游生态研究中采用了同样的原则，在那里我们已经有了关于远洋和底栖食物网的群落组成和大小光谱的非常详细的数据，但是具有更高的可复制性（Silwood公园的96个中游生态）。该项目还将有一个一致的实地工作组成部分，将在北半球沿火圈的五个不同的地热地点进行；这些国家包括：冰岛、格陵兰岛、阿拉斯加、堪察加半岛和斯瓦尔巴群岛。这些北极哨兵系统将作为由于全球变暖加剧而向极地迁移的物种的避难所。此外，研究这些系统将特别有趣，因为高纬度地区的地表温度预计将在下个世纪上升7.5摄氏度（IPCC, 2014）。了解这些食物网的结构和动态将是解决未来问题的基础，这些问题将出现在我们的纬度。这种地热系统的美妙之处在于，它们几乎就像室外实验室一样，事实上，溪流具有相似的化学成分，只是水温不同。冰岛的亨吉尔（Hengill）已经被研究了好几年，我们现在对它的食物网有了详细的描述。这将使我们能够将NGS技术应用于一个描述良好的食物网，我们希望在那里与从传统食物网分析中收集的数据相匹配，特别是在物种丰富度和丰度方面。除此之外，我将尝试描述一些在食物网分析中尚未被理解的联系，例如一些群体的饮食（例如食性捕食者），它们代表了食物网中缺失的一环。为了探索这些“缺失的环节”，我将应用NGS技术来分析从肠道内容分析中看不到的捕食者的饮食，这将使我们能够在食物网结构方面增加有价值的信息。冰岛的站点将作为一个平台，我们将在这里测试方法和实验，然后将这些方法和实验应用到所有其他地热站点。保持这些方法的一致性将是至关重要的，以便调查和理清将在不同地点出现的差异和潜在的共性。特别是，我们预计变暖将在物种差异很大的生态系统中产生类似的模式。最后，我将调查自然系统和生态系统之间的共性，因为之前的研究已经支持冰岛溪流和英国生态系统之间生态系统呼吸的一致热响应。

The aim of this project is to quantify the effects of global warming on food web structure of freshwater ecosystems. I will be studying the strength of the links, and the direction of energy flows of several different food webs across a temperature gradient. To address these key ecological questions I will test novel molecular techniques such as next generation sequencing (NGS) which will be used to match more traditional food web approaches. In particular, it is possible to identify species by sequencing part of their genetic code, and comparing it to a database without referring to their morphological traits. The use of such techniques gives us extremely valuable information, in fact: we can detect the presence of cryptic species (I) which are morphologically identical, but have distinct genetic traits, also, identify early instar larvae (II) which are impossible to distinguish at such stage, but it can be useful also in terms of damaged specimens (III). Moreover, I will take advantage of new mesocosm facilities at Silwood park in order to predict the effects of warming on the stability and structure of freshwater ecosystems, in particular we are aiming to heat mesocosms by 4C and 7C which is the degree of heat that we expect to encounter at our latitudes, and high latitudes, respectively, in the following century. The principle is the same adopted in a long-term mesocosm study in Dorset (UK) where we already have an exceptionally detailed data of the community composition and size-spectra of both the pelagic and benthic food webs, but with a higher replicability (96 mesocosms in Silwood park) of treatments. This project will also have a consistent fieldwork component which will take place in five different geothermal sites along the ring of fire in the Northern hemisphere; these will include: Iceland, Greenland, Alaska, Kamchatka, and Svalbard. These arctic sentinel systems will act as a refuge for species migrating polewards due to increase global warming. Moreover, it will be particularly interesting to study these systems as high latitudes surface temperatures are predicted to increase up to 7.5C in the following century (IPCC, 2014). Understanding structure and dynamics of these food webs will be fundamental to address future issues which will appear at our latitudes. The beauty of such geothermal systems is that they almost act as outdoor laboratories, in fact, streams have similar chemical composition, and only differ by water temperature. The Icelandic site (Hengill) has been studied for several years, and we now have a detailed description of its food web. This will allow us to apply NGS techniques into a well described food web, where we expect to match data collected from traditional food web analysis, particularly in terms of species richness and abundances. In addition to this, I will try to describe some of the links yet poorly understood in food web analysis, such as the diet of some groups (e.g. suctorial predators) which represent a missing link within the food web. In order to explore these "missing links", I will apply NGS techniques to analyse the diet of predators not visible from gut content analysis, this will allow us to add valuable information in terms of food web structure. The Icelandic site will act as a platform where we will be testing methods, and experiments which will be then applied to all the other geothermal sites. Keeping these methods consistent will be crucial, in order to investigate and disentangle differences and potential generalities which will emerge across the different sites. In particular, we expect warming to produce similar patterns in ecosystems with a wide difference of species. Finally, I will investigate generalities between natural systems and mesocosms, as previous studies already support a consistent thermal response in relation to ecosystem respiration between the Icelandic streams and the UK mesocosms.