Understanding the spatial and temporal dynamics of environmental DNA for monitoring and management of priority invasive species

外来入侵物种（INNS）是全球生物多样性丧失的五大驱动因素之一，生物入侵的速度正在增加。贻贝（斑马贻贝、多形贻贝和斑马贻贝）是英国监测和管理重点名单上的INNS，因为它们可能会迅速扩散，并对生物多样性、基础设施和人类健康产生负面影响（例如Karatayev等人，2015年）。德雷森德菌可以迅速占领坚硬的表面，通过堵塞管道和覆盖其他人工结构，给水工业和电力公司带来重大问题。仅在约克郡，每年从管道中去除斑马贻贝的费用就高达60万英镑。早期发现是防止INNS建立和进一步传播的关键，但这对具有微观生命阶段的物种尤其具有挑战性。环境DNA （eDNA）是一种敏感的新方法，它开始彻底改变我们监测INNS的方式（Lawson Handley 2015; Blackman et al. 2018）。我们最近开发了用于德莱森贻贝的eDNA检测方法，该方法对检测成虫和幼虫阶段都非常敏感（Blackman et al. 2018; Stroud 2018）。学生将使用这些工具来获得对德雷塞尼德eDNA动力学的新见解，并提高对物种分布和影响的理解。在学习期间产生的方法和数据对于促进德雷塞尼德病的监测、管理和缓解至关重要。目的1：了解Dreissenid eDNA的时间动态，并为未来的采样活动提供信息。eDNA的产生和降解率在一年中可能会有所不同，这是由于德雷森氏菌活动和种群动态的不同，以及水混合和紫外线等环境因素的不同。这些因素如何相互作用影响德雷赛尼eDNA的检测概率目前尚不清楚。该学生将使用场地占用模型来生成一年中不同时间的eDNA检测概率，确定哪些季节性变量会影响检测，并为未来的采样活动提供信息。目的2：了解eDNA分布的空间动态，确定哪些关键环境变量影响Dreissenid eDNA的检测概率。eDNA的检测受到环境的物理、化学和生物特性的影响（Barnes & Turner 2015）。该项目将研究环境变量（如底物类型、DOC叶绿素、pH值等）如何影响德莱森氏菌种群、eDNA的产生和持久性。不同的环境变量对eDNA检测概率的影响，将使用场地占用模型进行调查。目的3：利用eDNA鉴定德雷森菌传播的关键途径和载体。识别INNS传播的高风险媒介和途径对于制定管理计划至关重要，但对途径的研究往往受到当前低密度物种检测方法低功率的限制。该学生将使用eDNA方法来调查不同途径的相对重要性，并为途径管理计划提供信息，并探索使用原位检测方法进行快速，经济高效和敏感的监测。目的4：评价芦苇属植物对入侵生态系统结构和功能的影响。Dreissenids被认为对入侵群落有广泛的影响，对某些物种有积极影响，但对其他物种有减少作用（Churchill 2013; Ward & Ricciardi 2013），但它们的影响尚未在整个生态系统层面进行全面调查。该项目将利用DNA元条形码技术，结合全面的环境元数据，生成整个群落随时间和空间变化的数据，从而对入侵生态系统的结构和功能产生独特的影响。

Invasive non-native species (INNS) are one of the five global drivers of biodiversity loss and the rate of biological invasions is increasing. Dreissenid mussels (zebra mussels Dreissena polymorpha and quagga mussels D. rostriformis bugensis) are INNS that are high on the UK priority list for monitoring and management, due to their potential for rapid spread and negative impacts to biodiversity, infrastructure and human health (e.g. Karatayev et al. 2015). Dreissenids can rapidly colonise hard surfaces, causing major problems for the water industry and power companies by clogging pipes and encrusting other artificial structures. In Yorkshire alone, removal of zebra mussels from pipework currently costs £600K per annum. Early detection is key to preventing establishment and further spread of INNS, but this is particularly challenging for species that have microscopic life stages. Environmental DNA (eDNA) is a sensitive new method that is starting to revolutionise how we monitor INNS (Lawson Handley 2015; Blackman et al. 2018). We have recently developed eDNA assays for Dreissenid mussels that are highly sensitive for detection of both adult and larval stages (Blackman et al. 2018; Stroud 2018). The student will use these tools to obtain novel insights into the dynamics of Dreissenid eDNA and to improve understanding of the species' distribution and impact. Methods and data generated during the studentship will be critical for facilitating Dreissenid monitoring, management and mitigation.Objective 1: to understand the temporal dynamics of Dreissenid eDNA and inform future sampling campaigns. eDNA production and degradation rates are likely to vary throughout the year due to differences in Dreissenid activity and population dynamics, and environmental factors such as water mixing and UV. How these factors interact to influence detection probability of Dreissenid eDNA is currently unknown. The studentship will use site occupancy modelling to generate eDNA detection probabilities at different times of the year, determine which seasonal variables influence detection, and inform future sampling campaigns. Objective 2: to understand the spatial dynamics of eDNA distribution and determine which key environmental variables influence the probability of detection of Dreissenid eDNA. The detection of eDNA is influenced by the physical, chemical and biological properties of the environment (Barnes & Turner 2015). The studentship will investigate how environmental variables (e.g. substrate type, DOC chlorophyll, pH etc) effect Dreissenid populations, eDNA production and persistence. The impact of different environmental variables on the probability of eDNA detection, will be investigated using site occupancy modelling.Objective 3: to use eDNA to identify key pathways and vectors for Dreissenid spread. Identification of high risk vectors and pathways for INNS spread is essential for drafting management plans, but research into pathways is often limited by the low power of current methods to detect species at low density. The studentship will use eDNA methods to investigate the relative importance of different pathways and inform a pathway management plan, and also explore the use of in situ detection methods for rapid, cost-effective and sensitive monitoring. Objective 4: to evaluate the impact of Dreissenids on the structure and function of invaded ecosystems. Dreissenids are thought to have wide-ranging impacts on invaded communities, with positive effects on some species but reductions in others (Churchill 2013; Ward & Ricciardi 2013), but their impacts have not yet been comprehensively investigated at the whole ecosystem level. The studentship will generate data over time and space on entire communities, using DNA metabarcoding, which together with comprehensive environmental metadata, will allow unique insights into impact of Dreissenids on the structure and function of invaded ecosystems.