Evolution of dispersal and pollination in ecologically dominant grasses

北美的高草草原是一个标志性的景观，是美国历史的中心。 大草原的名字来自于那些构成东非广阔草原的草的近亲。 这些草为牲畜和野生动物提供食物，为鸟类提供栖息地;它们还从大气中吸收碳，并将其深埋在地下，在那里支持有益的微生物，使美国农业所依赖的肥沃土壤。 这个项目是密苏里州圣路易斯的唐纳德·丹佛斯植物科学中心的研究科学家、伊利诺伊州艾尔萨的普林西比亚学院的本科生和东非的同事们合作的，旨在揭示草传播花粉的方式，它们如何为种子提供碳，以及种子如何散布在整个景观中。 这些信息将告诉我们，草原将如何应对当前的干扰，如火灾，城市化和农田转换，以及未来气候变化造成的干扰。 该项目的重点是三个主要的草属，Andropogon，Schizachyrium和Hyparpalea，加上一些较小的相关属，共包括约250种，其中许多是生态优势。 研究人员将首先使用DNA序列来揭示该群体的系统发育历史，然后利用这一历史来追踪植物的种子部分如何随着进化时间的推移而变化，以及它们如何与气候、火和水分相关。 这些植物中的种子不会简单地从植物上脱落。 相反，它们是作为一个复杂的传播结构的一部分被释放出来的，这个结构包括花茎和叶状苞片。散布结构在大小、有无毛、有无雄花和雌花以及有无芒（苞片的吸湿性延伸）方面因种而异。 该结构可以是种子传播的适应，用于控制特定土壤类型中的发芽，或用于耐火。 然而，同样的结构也可能有助于授粉。 此外，在发育过程中，散布结构的许多部分是绿色的，并且可以为发育中的种子提供光合作用。 因此，该结构可以选择在三个不同的生活史阶段的功能：授粉，灌浆和传播。 这个项目将使用历史系统发育的方法和实验的方法来测试目前的功能的分散结构。 这里研究的扩散结构很像高粱、甘蔗和芒草，因此数据将适用于这些作物以及主要的草地物种。

The tallgrass prairie of North America is an iconic landscape, central to America history. The grasses from which the prairie takes its name are close relatives of those that make up the vast grasslands of eastern Africa. The grasses provide food for livestock and wild animals, and habitat for birds; they also pull carbon from the atmosphere and bury it deep in the ground where it supports beneficial microbes that make the rich soil on which American agriculture depends. This project is a collaboration between research scientists at the Donald Danforth Plant Science Center in St. Louis, Missouri, undergraduates at Principia College in Elsah, Illinois, and colleagues in eastern Africa, and is aimed at unraveling the ways the grasses spread their pollen, how they provide their seeds with carbon, and how the seeds are dispersed across the landscape. This information will tell us how the grasslands will respond in the face of current disturbance such as fire, urbanization, and conversion to farmland, and future disturbances caused by a changing climate. This project focuses on three major grass genera, Andropogon, Schizachyrium, and Hyparrhenia, plus a few smaller related genera, that together include some 250 species many of which are ecological dominants. Researchers will first use DNA sequences to uncover the phylogenetic history of the group, and then use that history to trace how the seed-bearing portions of the plant have changed over evolutionary time and how they correlate with climate, fire, and moisture. The seeds in these plants do not simply drop off the plant. Instead they are released as part of a complex dispersal structure that includes pieces of floral stalks and leaf-like bracts. The dispersal structure varies between species in size, presence or absence of hairs, presence of male and female flowers, and presence or absence of awns (hygroscopic extensions of bracts). The structure may be an adaptation for seed dispersal, for the control of germination in particular soil types, or for resistance to fire. However, the same structures may also help with pollination. In addition, many parts of the dispersal structure are green during development, and may provide photosynthate for the developing seed. Thus the structure could be selected for functions at three different life history stages: pollination, grain filling, and dispersal. This project will use both a historical phylogenetic approach and an experimental approach to test the current function of the dispersal structure. The dispersal structure studied here is much like that of sorghum, sugarcane and Miscanthus, so the data will apply to those crops as well as to the major grassland species.