Evolution of dispersal and pollination in ecologically dominant grasses

北美的高草大草原是美国历史中心的标志性景观。草原得名的牧草与构成东非广大草原的牧草是近亲。草为牲畜和野生动物提供食物，也是鸟类的栖息地；它们还从大气中吸收碳，并将其深埋在地下，在那里它支持有益的微生物，使美国农业所依赖的肥沃土壤变得肥沃。这个项目是密苏里州圣路易斯市唐纳德·丹福斯植物科学中心的研究科学家、伊利诺伊州埃尔萨市普林西亚学院的本科生和东非同事共同合作的项目，旨在揭开草传播花粉的方式，它们如何为种子提供碳，以及种子是如何分布在整个土地上的。这些信息将告诉我们，草原将如何应对当前的干扰，如火灾、城市化和退耕，以及未来气候变化造成的干扰。这个项目集中在三个主要的草属，仙人掌，裂谷草和水草属，加上一些较小的相关属，总共包括大约250种，其中许多是生态优势种。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，然后利用这段历史来追踪该植物的种子部分如何随着进化时间的推移而发生变化，以及它们与气候、火和水分的关系。这些植物中的种子不会简单地从植物上脱落。取而代之的是，它们作为复杂的扩散结构的一部分被释放，该结构包括花梗和叶状的苞片。散布结构因物种的大小、有无毛、雄花和雌花的存在以及芒的存在或不存在而有所不同(苞片的吸湿延伸)。该结构可用于种子传播、控制特定土壤类型的萌发或耐火。然而，同样的结构也可能有助于授粉。此外，散布结构的许多部分在发育过程中是绿色的，可能为发育中的种子提供光合作用。因此，该结构可以在三个不同的生活史阶段进行功能选择：授粉、灌浆和扩散。这个项目将同时使用历史系统学方法和实验方法来测试分散结构的当前功能。这里研究的扩散结构与高粱、甘蔗和芒属植物非常相似，因此这些数据不仅适用于主要的草原物种，也适用于这些作物。

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.