Dissertation Research: Balancing Costs and Benefits in a Mutualism: Conditionality in the Interaction Between the Grass, Hystris patula and its Fungal Endophyte

真菌内生菌与禾草之间的关系从寄生到共生，是研究相互作用条件的理想选择。随着时间的推移，种群中受感染植物的频率会增加；这经常被引用作为与种子内生菌相互作用是一种互惠关系的证据。假设受感染植物和未受感染植物的相对适应度是恒定的。如果相对适合度不同，草与真菌内生菌之间的相互作用可能处于微妙的平衡状态，并根据影响成本和收益的环境因素从共生转向寄生。本项目将测试几个假设影响感染和未感染植物相对适合度的因素。这些包括相关的草食动物丰度、植物资源和真菌内生菌株在决定植物成本和收益平衡方面的作用。目前对互惠关系中条件结果的程度、决定结果的机制或结果变化的后果知之甚少。如果没有这些信息，就很难解决有关共生生态的重要问题。由于许多植物物种，包括重要的农作物，都有相关的真菌内生菌，因此了解这些相互作用背后的机制也具有相当大的应用价值。

9520728 Martin Associations between fungal endophytes and grasses range from parasitic to mutualistic, and are ideal for studying the conditionality of interactions. Frequencies of infected plants in populations can increase over time; this is often cited as evidence that the interaction with seed-borne endophytes is a mutualism. The assumption is that relative fitnesses of infected and non-infected plants are constant. If relative fitnesses vary, the interaction between grasses and fungal endophytes may be delicately balanced, and shift from mutualism to parasitism depending upon environmental factors affecting costs and benefits. This project will test several factors that are hypothesized to affect the relative fitness of infected and non-infected plants. These include the roles of associated herbivore abundance, plant resources, and fungal endophyte strain in determining the balance of costs and benefits to the plant. Little is currently known about the extent of conditional outcomes in mutualisms, the mechanisms that determine outcomes, or the consequences of variation in outcome. Without this information it will be difficult to address important questions about the ecology of mutualisms. Since many plant species, including important agricultural crops, have associated fungal endophytes, understanding the mechanisms behind these mutualistic interactions also has considerable applied value.