International Research Fellowship Program: The Impact of Environmental Heterogeneity on Coevolution in a Tritrophic Plant-bacteria-phage Interaction

国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。 该计划的奖项提供了联合研究的机会，以及使用独特或互补的设施，专业知识和国外的实验条件。该奖项将支持博士布里特Koskella二十四个月的研究奖学金工作与博士安格斯Buckling在英国牛津大学（十三个月）和约翰汤普森博士在加州大学，圣克鲁斯（11个月）越来越明显的是，宿主和其寄生物之间的共同进化发生在相对较短的时间内，并且受到宿主和寄生物之间的相互作用的强烈影响。互动发生的环境。虽然环境条件影响物种间的相互作用是很清楚的，但是基因流如何在异质景观中形成共同进化的过程还有待解决。该项目采取了一种新的方法来实验共同进化分析，通过扩大成对共同进化的研究，包括与第三个物种在复杂的景观相互作用。PI和宿主将研究植物种群、植物病原菌丁香假单胞菌及其相关噬菌体之间的三营养相互作用。该系统是理想的建立在微生物水平上的共同进化事件的规模和幅度，因为噬菌体的传播影响细菌的运动和种群大小，从而影响细菌对宿主植物的影响。此外，由于每个物种直接受到周围环境条件的影响，并作为一个不断变化的环境中的其他两个相互作用的物种，他们将能够使用的三种方式的相互作用，研究景观异质性的共同进化过程的影响。通过精心控制的选择实验和自然种群调查的新组合，他们将系统地研究协同进化的地理镶嵌理论的每个组成部分，首先通过量化细菌运动性的程度，已知影响细菌毒力，以及相应的噬菌体生活史性状在宿主植物物种和种群之间的变化。通过建立一系列的人工协同进化实验P. erichingae和噬菌体之间的植物宿主环境的操作，在相互选择的变化和基因流的相对作用进行了评估。为了补充这一实验性的协同进化工作，也正在进行一项调查，对来自不同地理区域和宿主植物物种的自然种群中的噬菌体流行率、特异性和局部适应性进行调查。很少有研究经验性地探讨了物种相互作用过程中地理变异对互惠选择的相对重要性;因此，拟议的工作将大大扩展我们对环境条件变化如何影响宿主-寄生虫共同进化的理解。这项研究还将为噬菌体治疗在控制病原植物细菌中的新用途提供基础。 此外，该项目对病原体在复杂景观中的移动的关注，在面对大规模的、人为介导的作物病原体传播时，将特别提供信息。

0754399KoskellaThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four month research fellowship by Dr. Britt Koskella to work with Dr. Angus Buckling at the University of Oxford in the UK (thirteen months) and with Dr. John Thompson at the University of California, Santa Cruz (eleven months).It is becoming abundantly evident that coevolution between hosts and their parasites occurs in relatively short time periods and is strongly influenced by the environment in which the interaction is occurring. Although it is clear that environmental conditions influence species interactions, exactly how the process of coevolution is shaped by gene flow across a heterogeneous landscape is yet to be resolved. This project takes a novel approach to experimental coevolutionary analysis by scaling up studies of pairwise coevolution to include interactions with a third species across a complex landscape. The PI and hosts will examine a tritrophic interaction between plant populations, the plant pathogenic bacteria Pseudomonas syringae, and its associated bacteriophages. This system is ideal for establishing the scale and magnitude of coevolutionary events at a microbial level in that the spread of bacteriophage influences both the movement and population size of bacteria, and thus the impact of bacteria on the host plant. Furthermore, since each species is directly influenced by the surrounding environmental conditions and is itself acting as a changing environment for the other two interacting species they will be able to use the three-way interaction to examine the implications of landscape heterogeneity for the coevolutionary process. Through a novel combination of carefully controlled selection experiments and surveys of natural populations they will systematically examine each component of the Geographic Mosaic Theory of Coevolution, first by quantifying the extent to which bacterial motility, known to affect bacterial virulence, and corresponding phage life-history traits vary among host plant species and populations. By setting up a series of artificial coevolution experiments between P. syringae and phage in which the plant host environment is manipulated, the variation in reciprocal selection and the relative role of gene flow is being evaluated. To complement this experimental coevolution work, a survey of phage prevalence, specificity, and local adaptation across natural populations from different geographic regions and host plant species is also being performed. Few studies have empirically explored the relative importance of geographic variation for reciprocal selection during species interactions; the proposed work will therefore greatly expand our understanding of how changing environmental conditions affect host-parasite coevolution. This research will additionally provide the basis for a novel use of phage therapy in controlling pathogenic plant bacteria. Furthermore, the project's focus on pathogen movement across complex landscapes will be particularly informative in the face of large-scale, human-mediated dispersal of crop pathogens.