Market Dynamics in a Nitrogen-fixation Mutualism

植物和土壤微生物之间的营养共生对植物进化和生态系统功能至关重要，但我们对这些古老相互作用的进化动力学和持久性机制几乎一无所知。 互惠互动是许多生物普遍和必须的，但它们在欺骗面前的进化持久性在理论上令人困惑。 伙伴选择和伙伴忠诚是对付作弊者的机制，理论上可以让互惠持续下去。 最近在几种植物与传粉者的相互作用中发现了制裁作弊者的证据，这是一种伙伴选择形式。 市场模型假设合作伙伴的选择，并因此提供了有用的范式，了解进化动力学的互惠，其中个人试图进行互惠互利的资源贸易与多个人（市场）。 拟议中的研究将测试伴侣选择是否可以解释这种互利共生在野生豆科植物羽扇豆属和慢生根瘤菌（栖息在根瘤中的固氮细菌）中的进化持久性。 实现这些目标的第一步，在豆科植物根瘤菌相互作用的遗传变异，共生质量和植物适应性反应的综合分析。 我们的研究结果将开始构建一个框架，了解持久性和进化动力学这一重要的互惠。

Nutritional symbioses between plants and soil microbes are critically important to plant evolution and ecosystem function, yet we know almost nothing about the evolutionary dynamics and mechanisms of persistence of these ancient interactions. Mutualistic interactions are widespread and obligatory for many organisms, yet their evolutionary persistence in the face of cheating is theoretically puzzling. Partner-choice and partner-fidelity are mechanisms for dealing with cheaters, and can theoretically allow mutualisms to persist. Evidence for sanctions against cheaters, a form of partner-choice, has recently been uncovered in several plant-pollinator interactions. Market models assume partner choice, and hence offer useful paradigms for understanding the evolutionary dynamics of mutualisms in which individuals attempt to conduct mutually beneficial trade of resources with multiple individuals (the market). The proposed studies will test whether partner-choice can explain the evolutionary persistence of this mutualism in wild legumes of the genus Lupinus, and Bradyrhizobium, the nitrogen-fixing bacteria that inhabit their root nodules. Achieving these goals is the first step in an integrated analysis of genetic variation, symbiotic quality, and plant adaptive responses in the legume-rhizobium interaction. Our results will begin to construct a framework for understanding the persistence and evolutionary dynamics of this important mutualism.