Dissertation Research: Maintenance of Polymorphism in a Natural Plant-Pathogen Interaction

[701320 . Coley]植物和它们的病原体之间的关系还没有被很好地理解，然而这些系统提出了与进化生态学的基本问题有关的引人入胜的问题。这项研究将解决一个这样的主题，维持抗性和毒力多态性。本研究将对本地野生向日葵（Helianthus annuus）及其真菌锈病（Puccinia helianthi）多态性维持的各种假设进行综合调查。首先，一系列的花园实验将确定是否存在可检测的适应性成本与携带不必要的抗性或毒性等位基因有关。这样的代价可能会平衡抗性和毒性的好处，从而产生多态种群。此外，将在自然种群中检验抗性的直接和间接适应度效益。罕见抗性或毒力基因型的频率依赖优势可能对多态性的维持也很重要，将进行对照花园实验来验证这一假设。最后，对犹他州自然种群的调查将比较对锈病有利或不利的地区的多态性，并将检查不同大小和隔离程度的种群中的多态性。提出的研究将严格测试各种关于维持毒力和抗性多态性的假设，并将对我们理解自然植物-病原体系统的进化动力学做出有价值的贡献。

9701320 Coley The relationships between plants and their pathogens are not well understood, yet these systems present fascinating questions which bear upon fundamental issues of evolutionary ecology. This research will address one such topic, the maintenance of resistance and virulence polymorphisms. This study will undertake an integrated investigation of various hypotheses for the maintenance of polymorphism in the native wild sunflower (Helianthus annuus) and its fungal rust (Puccinia helianthi). First, a series of garden experiments will determine whether there are detectable fitness costs associated with bearing unnecessary resistance or virulence alleles. Such costs might balance the benefits of resistance or virulence, resulting in polymorphic populations. In addition, both direct and indirect fitness benefits of resistance will be examined in natural populations. A frequency-dependent advantage for rare resistance or virulence genotypes might also be important to the maintenance of polymorphism, and a controlled garden experiment will be performed to test this hypothesis. Finally, surveys of natural populations in Utah will compare polymorphism in areas favorable or unfavorable for the rust, and will examine polymorphism in populations of differing sizes and degrees of isolation. The proposed research will critically test a variety of hypotheses for the maintenance of virulence and resistance polymorphisms, and will make a valuable contribution to our understanding of the evolutionary dynamics of natural plant-pathogen systems.