Towards 'crop-pollinating' landscapes: quantifying pollen supply and demand to manage wild pollinators for their benefits to food production

世界上四分之三的重要作物或35%的粮食产量依赖于动物传粉者。这包括许多水果、蔬菜、坚果和油。最近，科学家们发现，世界上大多数作物授粉是由一小群蜜蜂物种完成的，它们被称为“优势作物授粉者”。在英国，不超过20个物种承担了大部分的工作。一种是蜜蜂，由养蜂人饲养。其他的是常见于农田的野生物种。然而，在每个地方发现的野生蜜蜂种类的数量都在下降。这种下降的主要原因之一是乡村野花的减少，这在20世纪的英国是戏剧性的。特别是，豌豆和豆科开花植物的消失，它们有富含蛋白质的花粉，被认为给野生蜜蜂物种带来了麻烦。蜜蜂完全依靠花朵中的食物——花蜜和花粉——来生存和养育后代。花蜜是一种糖浆，为它们提供飞行和生长的能量。花粉提供了大部分蛋白质，这是幼虫生长的重要资源。帮助传粉者的一种方法是种植额外的花朵。这已被证明可以增加作物主要传粉媒介的数量，甚至可以提高作物产量。目前，科学家们不知道野生蜜蜂在一年中的不同时期需要多少花粉，或者需要什么类型的花粉来生存，也不知道现有的景观已经提供了多少花粉。一些人认为，一年中有一些特定的时间，比如早春或夏末，花粉特别少，增加花朵真的会帮助蜜蜂。本研究采用了非常新颖的科学技术来量化农田花粉的需求和供应。一个令人兴奋的进展是，科学家们刚刚建立了一个数据库，其中包含了所有1479种英国本土植物的DNA序列。这使得通过将花粉放入测序机来识别蜜蜂采集的花粉中的植物物种成为可能。这叫做DNA元条形码。对蜜蜂的早期研究结果表明，树木的花粉在年初可能比之前认为的更重要。这项研究将记录红尾蜂和早期大黄蜂群体在至少两年内使用的所有植物。在实验室里对大黄蜂进行的一系列实验将测试需要多少和什么样的花粉来培养个体幼虫，或提供一个健康的群体。将这些信息与它们在真实景观中选择的花粉来源相结合，将使我能够准确地计算出这些为作物授粉的大黄蜂对花粉的需求。为了量化一个农田的花粉供应，我将使用借鉴细胞生物学的图像处理技术，通过照片来测量春、夏、秋三个季节每种类型的花的数量。这个想法是建立一个易于使用的软件，告诉农民确切地种植什么花，这样他们的农场就能支持一个繁荣的野生传粉者社区，为他们的庄稼提供可靠的授粉。该软件将每月比较花粉供应和花粉需求。能够测量农田区域的花粉供应和需求将使科学家能够回答关于传粉媒介的持续争论的一个基本问题：目前是什么限制了野生传粉媒介的数量？可用的蛋白质（花粉）是主要的限制因素，还是碳水化合物（花蜜）、筑巢地点、越冬死亡率或杀虫剂或疾病的负面影响？我研究的总体目的是验证花粉是农业景观限制因素的假设。如果正确的话，那么我们能为传粉者做的最好的事情就是种花。如果这是错误的，并且其他因素限制了传粉媒介的数量或导致了数量的下降，那么就需要采取不同的策略来保留辛勤工作的野生传粉媒介的可行群落，以支持粮食生产。

Three quarters of the world's important crops, or 35% of all food produced by volume, depends on animal pollinators. This includes many fruits, vegetables, nuts and oils. Recently, scientists have found that most crop pollination in the world is carried out by a small group of bee species, called the 'dominant crop pollinators'. In the UK, no more than 20 species are doing most of the work. One is the honey bee, kept by beekeepers. The others are wild species found commonly in farmland.Yet numbers of wild bee species found in each place are declining. One of the main reasons for this decline is loss of wild flowers in the countryside, which was dramatic in the twentieth century in the UK. In particular, the loss of flowering plants in the pea and bean family, which have protein-rich pollen, is thought to have caused trouble for wild bee species. Bees rely entirely on food from flowers - nectar and pollen - to survive and raise their young. Nectar is a sugar syrup, and provides them energy to fly and grow. Pollen provides most of the protein, a crucial resource for growing larvae. One way to help pollinators is by planting extra flowers. This has been shown to increase the numbers of dominant crop pollinators, and can even lead to improvements in crop yield. At the moment scientists don't know how much, or what types of pollen wild bees need to survive at different times of year, and have very little idea how much pollen is already supplied by existing landscapes. Some think there are particular times of year, such as early spring or late summer, when pollen is especially limiting, and adding flowers would really help bees.This research uses very new scientific techniques to quantify the demand for and supply of pollen in farmland. One exciting development is that scientists have just made a library of DNA sequences from all 1,479 of UK native plants. This makes it possible to identify plant species in bee-collected pollen, by putting the pollen into a sequencing machine. It's called DNA metabarcoding. Early results for honey bees show that pollen from trees could be more important at the start of the year than was previously thought. This research will document all the plants that red-tailed and early bumblebee colonies use over at least two years.A series of experiments with bumblebees in the laboratory will test how much and what kind of pollen are needed to raise individual larvae, or supply a healthy colony. Combining this information with the pollen sources they choose in real landscapes will allow me to accurately calculate pollen demand by these crop-pollinating bumblebees.To quantify pollen supply in an area of farmland, I will use image processing techniques borrowed from cell biology to measure how many flowers of each type there are through spring, summer and autumn, using photographs. The idea is to build an easy-to-use piece of software to tell farmers exactly what flowers to plant so their farm supports a thriving wild pollinator community that provides reliable pollination to their crops. The software will compare pollen supply with pollen demand on a monthly basis.Being able to measure pollen supply and demand in an area of farmland will allow scientists to answer a fundamental question central to ongoing debates about pollinators: What currently limits wild pollinator populations? Is available protein (pollen) the main limiting factor, or is it carbohydrate (nectar), nesting sites, overwinter mortality or negative impacts of pesticides or disease? The overall aim of my research is to test the hypothesis that pollen is the limiting factor in agricultural landscapes. If correct, then the best thing we can do for pollinators is plant flowers. If it is wrong, and something else is limiting pollinator numbers or causing declines, then different strategies will be necessary to retain viable communities of hard-working wild pollinators that support food production.