Analyzing historical plant-pollinator interactions by conducting pollen metabarcoding on museum specimens of German bumblebee species

在德国有35种以上的非寄生花粉采集熊蜂，其中20%是重要的传粉者，16种是稀有或濒临灭绝的。近几十年来，许多大黄蜂物种的数量急剧下降，主要是由于土地利用的变化和农业实践的变化。通过对荷兰、比利时和英国野生蜜蜂尸体上所含花粉的显微鉴定，对自然历史收集的宿主植物使用进行了历史分析，结果显示，首选宿主植物物种的减少是野生蜜蜂减少的主要原因（Kleijn和Raemakers，2008年; Scheper等人，2014年）。DNA元条形码分析目前允许以更高的分辨率和更深的深度增强花粉识别过程（Pornon等人，2016）。我们的目标是通过使用和优化DNA元条形码技术在三个时间段（1950年之前，1950-1980年之间，1980年之后，农业实践的重大转变）对所有德国熊蜂物种进行花粉鉴定，从而有效地利用这一点。一个涉及动物学家，植物学家和生态学家的跨学科项目将（i）增强当前用于花粉DNA元条形码的软件，以减少与方法相关的偏差（ii）通过使用多个标记提高分类分配的准确性，（iii）通过从自然历史收集中取样，以回顾性的方式分析常见和罕见的德国熊蜂物种的觅食偏好，以及（iv）评估植物可用性是否是二十世纪熊蜂种群趋势的潜在驱动力，并可作为当前物种稀有性或丰度的解释。

More than 35 nonparasitic pollen collecting bumblebee species occur in Germany, 20 percent of which are important pollinators and 16 are rare or threatened with extinction. Many bumblebee species populations have dramatically declined in recent decades primarily due to land use changes and changes in agricultural practices. Historical analyses of host plant use from natural history collections by microscopic identification of pollen contained on the bodies of wild bees from the Netherlands, Belgium and Britain revealed the decline of preferred host plant species to be the main driver for wild bee decline (Kleijn and Raemakers 2008, Scheper et al. 2014). DNA metabarcoding analyses currently allows for enhancing the pollen identification process with higher resolution and in more depths (Pornon et al. 2016). Our aim is to make efficient novel use of this by using and optimizing DNA-metabarcoding technologies for pollen identification on all German bumblebee species across three time periods (before 1950, between 1950-1980, after 1980, indicative of major shifts in agricultural practices). An interdisciplinary project involving zoologists, botanists and ecologists will (i) enhance the current software used for pollen DNA-metabarcoding to reduce method-related biases (ii) improve accuracy of taxonomic assignments through multiple marker usage, (iii) analyze foraging preferences of common and rare German bumblebee species in a retrospective manner by sampling from natural history collections, and (iv) evaluate if plant availability is the potential driver of twentieth century bumblebee population trends and could serve as an explanation of current species rarities or abundances.