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

MacHair是位于苏格兰西部和爱尔兰西北部的一种独特的环境，其特点是低海拔的沿海草原通常前面有更高的沙丘脊线。马海毛受到海洋资源的高度补贴，经常与各种各样的淡水水体相连。因此，MacHair在海洋和淡水集水系统之间扮演着重要的缓冲和纽带的双重角色。此外，由于沙质土壤提供了相对较好的农业潜力，马海毛已被广泛用于农田农业(1)。马海毛栖息着各种各样的野生动物，其中一些物种的动植物处于高度保护的优先地位。特别令人感兴趣的是一群令人着迷的昆虫传粉者(大黄蜂和独居蜜蜂)，它们现在很大程度上依靠马海毛野花在不列颠群岛生存。值得注意的是，富有魅力的大黄蜂在英国已经严重衰落，现在只能在苏格兰的西部和北部边缘地区找到。这些蜜蜂为许多马海毛野花提供基本的授粉服务，因此它们的生存和健康是保护马海毛本身的关键。耐盐植物(如生长在马海毛中的植物)通常会在它们的组织中积累高水平的钠，这对大黄蜂特别有吸引力，对它们特别有利，因为大黄蜂和所有其他传粉者一样，通常很难从食物中获得足够的钠(2)。黄毛花有可能为它们的大黄蜂传粉者提供更高的钠奖励，这加强了这两种生物之间复杂的互惠互利关系。这个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和马海毛之间的复杂关系，并利用这种理解来预测未来的气候变化和人类管理可能如何影响这个脆弱的生态系统。学生将从查看历史数据开始他们的研究，以推断马海毛的植物群落和传粉者群落如何随着时间的推移在不同地区发生变化，并将这与不同物种产生花蜜和花粉的最新信息联系起来(目标1)。一些初步证据表明，昆虫授粉的植物在马海毛中总体上减少了(除了一些特殊的例外)，而风媒植物变得更加普遍(3)。下一步将是确定马海毛植物中自然存在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对环境中不同水平的钠的反应(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普通花园中不同钠制度下饲养的植物的反应，来描述大黄蜂传粉者对马海毛的适应情况(目标3)。最后，学生将结合以前目标中的历史、观察和实验数据来预测环境条件的变化(例如气候变化导致的海洋入侵增加)将如何影响马克海毛中的钠水平，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)