Factors limiting marine connectivity at a species' range edge - the case of the pink sea fan, Eunicella verrucosa

粉红色的海扇，疣状Eunicella，被列入IUCN红色名单，是英国水域的保护物种。它被列为受保护的特征，是2013年和2016年在英格兰西南部指定的许多MCZ指定的关键因素。了解该物种的多样性和连通性对于保护该物种和指定更多的候选MCZ至关重要(自然英格兰，2016)。我们预计，这项研究将对这两个关键因素提供信息。拟议的项目将调查基因流动的海洋途径和障碍的程度，例如由于潮汐混合锋和海岸/河口环流模式等残余洋流，以及选择在英国西南部粉红海扇种群之间的遗传差异中所起的作用。疣虫是一种广播性产卵者，幼虫依靠洋流扩散，然而，到目前为止，人们对该物种的基本生物学知之甚少，对其在水柱中的保留时间或应对热应激的能力知之甚少。因此，我们将进行模型和水族馆研究，以开始探索可能导致缺乏招募到这些范围边缘种群的关键生物学因素。明显的研究途径包括：热应激、影响产卵时间的因素、产卵持续时间、在水柱中的存活率和浮游幼体的持续时间。当这些数据可用时，这些数据随后可以被参数化为我们的海洋模型。将使用高质量的物理(电流、温度)和生物(如种群分布、幼虫行为)数据来验证模型的真实性，并将设计一个敏感性框架，将扩散/连通性结果设定在基于自然变异性和模型参数的不确定范围内。我们在埃克塞特拥有从大西洋东北部和地中海西部物种范围内收集的海扇组织样本的广泛选择，对于这一提议至关重要的是，我们现在已获得许可，可以与威尔士彭布罗克郡斯科默海洋保护区的NRW工作人员合作，从最近在斯科尔海洋保护区内定居的新兵身上采集组织样本。一个关键的目标将是确定在Skmer招募新海迷的低水平是否是由于连通性、选择(可能是温度，特别是冬季最低温度)，或者是否是(或在多大程度上)Allee效应在起作用，即成熟成年球迷的人口密度现在非常低(很少有粉丝，分布广泛)，以至于配子找到彼此的机会降低到一个尚不清楚的临界阈值以下。斯科默的发现将与伦迪的发现进行比较，伦迪位于相似的纬度，但与康沃尔郡北部和西部以及锡利岛的主要粉色海扇群体的水中连接可能更强劲。我们将使用一种称为RAD-SEQ的分子技术来识别与特定地理区域和/或特定选择压力相关的单核苷酸多态(SNPs)基因座。我们正在进行的项目(Exeter)最近完成了对粉红色海扇基因组中数千个SNPs的筛选--将根据它们区分感兴趣人群的能力(基于FST)选择一组最具鉴别力的SNPs。总之，该项目为研究生提供了独特的跨学科研究培训，有机会获得敏感海洋生物的分子遗传学、海洋建模和水族馆操作方面的经验，产生的结果将通过我们的CASE合作伙伴自然英格兰和我们的合作伙伴自然资源威尔士直接提供给英国海洋政策。这样的组合应该会培养出一名技能高超、能胜任工作的年轻研究员。

The pink sea fan, Eunicella verrucosa, is IUCN red-listed and is a protected species in UK waters. It is listed as a Protected Feature, a key factor in the designation of many of the MCZs designated in southwest England in 2013 and 2016. An understanding of the diversity and connectivity of this species is essential for both conservation of the species and the designation of further candidate MCZs (Natural England, 2016). We anticipate that this research will inform on both these key factors. The proposed project will investigate the extent of oceanographic pathways and barriers to gene flow, e.g. due to residual currents such as tidal mixing fronts and coastal/estuarine circulation patterns, and the role of selection in driving genetic differences between populations of pink sea fan at the northern limit of its range in southwest Britain. E. verrucosa is a broadcast spawner, with larvae reliant on oceanic currents for dispersal, and yet, to date, very little is known about the basic biology of this species, with little or no knowledge of its retention time in the water column or its ability to deal with thermal stress. Accordingly, we will undertake modelling and aquarium studies to begin to explore key biological factors that might be contributing to the lack of recruitment into these range edge populations. Obvious avenues for investigation include: heat stress, factors affecting spawning time, spawning duration, survival in the water column and pelagic larval duration. As these data become available these can subsequently be parameterised into our oceanographic models. High quality physical (currents, temperatures) and biological (e.g. population distributions, larval behaviour) data will be used to ground-truth the models, and a sensitivity framework will be designed to set the dispersal/connectivity results within uncertainties based on natural variability and model parameterisations. We hold at Exeter an extensive selection of sea fan tissue samples collected from across the species' range in the northeast Atlantic and the western Mediterranean and, critical to this proposal, we have now obtained permission to work with NRW staff at the Skomer Marine Reserve in Pembrokeshire, Wales, to take tissue samples from new recruits which have recently settled within the Skomer Marine Reserve. A key objective will be to establish whether the low level of recruitment of new sea fans at Skomer is due to connectivity, selection (possibly temperature, esp., minimum winter temperature), or whether (or to what extent) the Allee effect is acting, whereby the population density of mature adult fans is now so low (few fans, widely spaced) that the chances of gametes finding each other are reduced below an as yet unknown critical threshold. Findings for Skomer will be compared with those obtained at Lundy, a site at a similar latitude, but with potentially more robust in-water connectivity to major populations of pink sea fan in north and west Cornwall and the Isles of Scilly. We will use a molecular technique known as RAD-seq to identify single nucleotide polymorphism (SNPs) loci associated with particular geographical regions and/or with particular selection pressures. Our on-going project (Exeter) has recently finalised the screening of several thousand SNPs from across the pink sea fan genome - a panel of the most discriminating SNPs will be selected based on their ability to discriminate populations of interest (based on FST). In summary, the project offers a unique, trans-disciplinary research training for a postgraduate student with opportunities to gain experience in molecular genetics, oceanographic modelling and aquarium manipulations of sensitive marine organisims, generating results that will feed directly into UK marine policy through our CASE partner, Natural England, and our associate partner, Natural Resources Wales. Such a mix should deliver a highly skilled and employable young researcher.