Importance and sustainability of endangered communities of bee pollinators in the machair, a changing coastal ecosystem

马沙尔是苏格兰西部和爱尔兰西北部的一个独特环境，其特点是低水平的沿海草原，前面通常是较高的沙丘脊。马沙尔由海洋资源提供大量补贴，通常与各种淡水水体相连。因此，马沙尔扮演着重要的双重角色，既是海洋和淡水集水系统之间的缓冲和连接。此外，由于沙质土壤具有较好的农业潜力，马沙尔已被广泛用于耕地农业(1)。各种各样的野生动物栖息在马沙尔，其中一些植物和动物物种受到高度保护。特别令人感兴趣的是一群迷人的昆虫传粉者（大黄蜂和独居蜜蜂），它们现在在不列颠群岛上主要依靠马毛野花生存。值得注意的是，有魅力的大黄大黄蜂在英国已经严重减少，现在只能在苏格兰的西部和北部边缘找到。这些蜜蜂为许多马毛野花提供了基本的授粉服务，因此它们的生存和健康是马毛本身保存的关键。耐盐植物（比如那些生长在马毛里的植物）通常会在它们的组织中积累大量的钠，这对大黄蜂特别有吸引力和好处，因为大黄蜂和其他授粉者一样，通常很难从食物中获得足够的钠。有可能马毛花为它们的大黄蜂传粉者提供了更高的钠奖励，这加强了将这两种生物联系在一起的复杂互惠互利关系。本博士项目将从景观生态学和昆虫生理学的角度研究大黄蜂与马毛的复杂关系，并利用这一认识来预测未来气候变化和人类管理如何影响这一脆弱的生态系统。学生将通过查看历史数据来开始他们的研究，以推断马毛的植物和传粉者群落如何随着时间的推移在不同地区发生变化，并将其与不同物种的花蜜和花粉生产的最新信息联系起来（目标1）。一些初步证据表明，在马可毛地区，昆虫传粉的植物总体上减少了（除了一些特别的例外），而风传粉的植物变得更加普遍(3)。下一步将是表征天然存在于马毛植物中的钠和其他营养物质的水平，然后在实验室中测试一些关键植物物种如何对环境中不同水平的钠做出反应（目标2）。然后，学生将通过观察大黄蜂的觅食偏好以及它们在分子和生理水平上对在普通花园设置中不同钠浓度下饲养的植物的反应，描述大黄蜂传粉者对马毛的适应特征（目标3）。最后，学生将结合以往目标的历史、观测和实验数据，预测不断变化的环境条件（例如气候变化引起的海洋入侵增加）将如何影响马毛中的钠含量，从而影响当地蜜蜂传粉者的群落（目标4）。(1)安格斯海洋和海岸管理（2018）(2)米切尔总环境科学（2020）(3)刘易斯·奥科斯（2014）

The machair is a unique environment localised in Western Scotland and North-west Ireland, characterised by low-level coastal grasslands usually fronted by a higher dune ridge. The machair is highly subsidised by marine resources and often connects to a wide range of freshwater bodies. Thus, machair plays an important dual role as both buffer and link between ocean and freshwater catchment systems. In addition, due to sandy soils providing relatively good agricultural potential, machair has been used extensively for arable agriculture(1). A varied wildlife inhabits the machair, with some species of flora and fauna of high conservation priority. Of particular interest is a fascinating group of insect pollinators (bumblebees and solitary bees) that now largely depend on the machair wildflowers for their survival in the British Isles. Notably, the charismatic Great Yellow bumblebee has seriously declined in the UK and can now be found only in western and northern fringes of Scotland. These bees provide fundamental pollination services to many machair wildflowers, and therefore their survival and health is key for the preservation of the machair itself. Salt-tolerant plants (like those growing in the machair) typically accumulate high levels of sodium in their tissues and are particularly attractive and beneficial for bumblebees that normally struggle, as do all other pollinators, to gain enough sodium from their diet(2). It is possible that machair flowers provide higher sodium rewards to their bumblebee pollinators and this reinforces the complex reciprocal mutualism linking these two types of organisms. This PhD project will investigate the complex relationship linking bumblebees and the machair from a landscape ecology and insect physiology perspective, and use this understanding to predict how future climate change and human management might impact this fragile ecosystem. The student will start their research by looking at historic data to infer how plant and pollinator communities of the machair have changed over time in different areas, and link this to recent information on nectar and pollen production by different species (OBJECTIVE 1). Some preliminary evidence suggests that insect-pollinated plants have decreased overall in the machair (with some extraordinary exceptions), while wind-pollinated plants have become more prevalent(3). The next step will be to characterise the levels of sodium and other nutrients that naturally occur in machair plants, and then test in the lab how some key plant species respond to varying levels of sodium in the environment (OBJECTIVE 2). The student will then characterise the adaptation of bumblebee pollinators to the machair, by looking at their foraging preference and their response at the molecular and physiological levels to plants reared under different sodium regimes in a common garden setup (OBJECTIVE 3). Finally, the student will combine historical, observational and experimental data from previous objectives to predict how changing environmental conditions (for example increasing sea incursions caused by climate change) will affect sodium levels in the machair and, as a consequence, the communities of local bee pollinators (OBJECTIVE 4).(1)Angus Ocean and Coastal Management (2018)(2)Mitchell Science of The Total Environment (2020)(3)Lewis Oikos (2014)