Investigating drivers of marine connectivity in the pink sea fan: implications for its conservation and the designation of Marine Protected Areas

此前，我们与自然英格兰合作，研究了两种软珊瑚（Eunicella verrucosa； Ever和Alcyonium digitatum； Adig），它们来自英国和爱尔兰各地，以及欧洲西北部更远的地方。我们为这些八珊瑚开发了新的遗传标记（微卫星），并用14个（Ever）和11个位点（Adig）进行了分型。我们证明了英国和欧洲西北部水域的Ever（粉红海扇）种群显示出明显的区域遗传结构（Holland & Stevens, 2014, 2017；图1A）。相比之下，居住在大致相同地理区域的Adig（死者手指）样本出现了泛疫，并且没有表现出显著的遗传群体结构。然而，尽管这两个物种在英国西南部和爱尔兰周围的水域重叠，但分布图表明，该地区是Ever的北部界限，而Adig的南部界限。对Ever种群结构可能驱动因素的调查确定了两个处于选择状态的位点；在Adig中没有发现选择的证据。重要的是，进一步的分析排除了被选择的基因座，导致Ever数据集中的结构消失（图1B）；这一发现突出了选择在驱动该物种表观种群结构方面的潜在重要性。观察到的遗传结构模式是由连通性/连通性障碍还是由选择驱动的，这对我们了解这些物种的连通性以及海洋保护区的位置和间距，特别是对世界自然保护联盟（IUCN）列出的物种粉海扇来说，具有重要意义。这两个物种都被认为是传播产卵，幼虫依靠洋流传播，然而我们的研究结果表明，在同一地理区域，它们的连通性模式截然不同。迄今为止，人们对这些生物的基本生物学知之甚少，对它们应对热应激的能力也知之甚少。拟议的项目将调查两个物种种群之间遗传差异的选择程度，Ever在其活动范围的北部极限，Adig在其活动范围的南部极限。我们将探讨它们在基础生物学上的根本差异，以阐明可能导致所观察到的遗传结构模式显著不同的生物学因素，无论是由于连通性的差异还是由于选择的差异。在没有发表的八珊瑚基因组的情况下，我们将使用一种称为RAD-seq的分子生物学技术来识别特定于地理区域和/或选择（在埃克塞特）的位点。分子分析将由普通的花园实验和可控海洋中环境（普利茅斯海洋实验室）的热应力暴露来补充。疣状eununicella verrucosa是世界自然保护联盟的红色名录，是英国水域的受保护物种。它被列为受保护的特征，这是2013年和2016年英格兰西南部指定的许多mcz的关键因素。了解该物种的多样性和连通性对于物种保护和进一步候选mcz的指定至关重要（Natural England, 2016）。我们预计这项研究将为这两个关键因素提供信息。

Previously, in collaboration with Natural England, we studied two species of soft coral (Eunicella verrucosa; Ever and Alcyonium digitatum; Adig) from sites around Britain and Ireland, and from further afield in northwest Europe. We developed novel genetic markers (microsatellites) for these octocorals and typed them with panels of 14 (Ever) and 11 loci (Adig). We demonstrated that populations of Ever (the pink sea fan) in waters around Britain and northwest Europe showed marked regional genetic structure (Holland & Stevens, 2014, 2017; Figure 1A). In contrast, samples of Adig (dead man's fingers) inhabiting approximately the same geographic area appeared panmictic, and exhibited no significant genetic population structure. However, while both species overlap in the waters around southwest Britain and Ireland, distribution maps indicate that this area is the northern limit for Ever and the southern limit for Adig. Investigation of the possible drivers of population structure in Ever identified two loci as being under selection; no evidence of selection was detected in Adig. Critically, further analysis excluding the loci under selection resulted in the disappearance of structure from the Ever data set (Figure 1B); such a finding highlights the potential importance of selection in driving apparent population structure in this species. Whether the patterns of genetic structure observed are driven by connectivity/barriers to connectivity or by selection has major importance for our understanding of connectivity in these species and for the placement and spacing of marine protected areas, especially for the pink sea fan, an IUCN listed species. Both species are thought to broadcast spawn, with larvae reliant on oceanic currents for dispersal, yet our findings suggest very different patterns of connectivity across the same geographical area. To date, very little is known about the basic biology of these creatures, with little or no knowledge of their ability to deal with thermal stress. The proposed project will investigate the extent of selection driving genetic differences between populations of the two species, Ever at the northern limit of its range, Adig at its southern limit. We will explore fundamental differences in their basic biology to elucidate biological factors that might be contributing to the markedly different patterns of genetic structure observed, whether due to differences in connectivity or to selection. In the absence of published octocoral genomes, we will use a molecular biology technique known as RAD-seq to identify loci specific to geographical regions and/or under selection (at Exeter). The molecular analysis will be complemented by common garden experiments and heat stress exposures in a controllable marine mesocosm (at Plymouth Marine Laboratory). 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.