Do Symbioses Determine Plant Species Abundances? How Endophytic Fungi May Control Rarity, Dominance, and Invasiveness of Grasses

物种的数量从根本上说是不同的，从联邦濒危物种到杂草丛生的入侵者。已经提出了几种假说来解释这种模式，但没有一种能充分解释观察到的变化。在某种程度上，这一失败可能反映了这样一个事实，即微生物共生(微生物和植物之间广泛存在的互惠关系)在很大程度上被忽视了。这项建议通过评估微生物共生在控制稀有性和侵入性方面的作用，形成了一个新的方向。利用草和微生物内生菌(生活在植物叶片内的真菌)之间的实验上容易驯化的共生体，拟议的实验和人口统计模型测试共生体是否以及如何增加宿主的丰度。在牧草中，内生菌可能通过产生对昆虫和哺乳动物有毒的生物碱来提高寄主对草食的抗性，也可能增强寄主的抗旱性。对稀有和常见草种配对的比较实验将检验以下预测，即共生体对常见寄主物种的益处大于稀有寄主物种，并在本地和非本地寄主之间存在差异，从而提供迄今对草-内生植物共生生态最全面的研究。更清楚地了解内生菌生态可以为稀有植物保护和入侵植物控制(例如，通过内生菌的添加或消除)提供新的策略。通过在印第安纳州和德克萨斯州建立的网络，信息将被广泛地传达给州机构、保护区管理人员、种子公司和保护组织。这项工作还将通过培训研究生和本科生以及将当代研究带入课堂，将教学和研究结合起来。

Species fundamentally vary in their abundance, spanning a range from federally endangered species to severely weedy invaders. Several hypotheses have been proposed to explain this pattern, but none sufficiently account for observed variation. In part, this failure might reflect the fact that microbial symbioses (widespread, mutually beneficial associations between microbes and plants) have been largely ignored. This proposal forges a new direction by evaluating the role of microbial symbioses in governing rarity and invasiveness. Taking advantage of the experimentally tractable symbioses between grasses and microbial endophytes (fungi that live within plant leaves), proposed experiments and demographic models test whether and how symbionts increase host abundance. In grasses, endophytes may improve host resistance to herbivory through the production of alkaloids toxic to insects and mammals and also may enhance host drought tolerance. Comparative experiments on paired rare and common grass species will test predictions that symbionts benefits are greater for common than rare host species and differ between native and non-native hosts, providing the most comprehensive study to date on the ecology of grass-endophyte symbioses. A clearer understanding of endophyte ecology can offer novel strategies for rare plant conservation and invasive plant control (e.g., via endophyte additions or eliminations). Through networks established in both Indiana and Texas, information will be broadly communicated to state agencies, preserve managers, seed companies, and conservation organizations. The work will additionally integrate teaching and research, by training graduate and undergraduate students as well as bringing contemporary research into the classroom.