Ecology and evolution of the mycorrhizal mutualism in a changing environment

生物学家试图解释为什么有机体进化出如此多不同的形式和功能，并解释这种多样性如何影响生态群落的组装和功能。长期以来，人们一直将气候和竞争和捕食等敌对相互作用作为进化和生态变化的原因进行研究，但很少有人认识到，尽管同样常见，但相互作用是伙伴交换资源和服务以实现互利的相互作用。几乎所有的有机体都参与了一种或多种互惠关系，据预测，如果没有这些相互作用，地球上支持的物种将会少得多。植物与寄生于菌根真菌的根之间的相互作用是自然界中最古老和最广泛的互惠关系之一，在4亿多年前就开始演化。几乎所有的植物都被这些真菌侵占，它们增加了植物对土壤养分的获取，特别是磷，以换取光合作用中的糖。尽管植物对真菌接种具有互惠共生的特点，但它们对真菌接种的反应是多种多样的，从中性到对植物生长的100倍刺激。这项拟议的研究将在实验上测试为什么植物和菌根真菌之间的互惠关系在自然界中不同，以及这种差异如何影响植物群落的多样性和功能。首先，我们将使用受控自然选择实验来识别导致互惠关系进化变化的环境因素。其次，我们将检验互惠共生强度的差异是否会对种群动态和物种共存产生影响。第三，我们将测试人类活动中氮的广泛沉积是否会导致植物种群与菌根真菌进化出更强的互惠关系，然后测试这种进化是否会影响营养循环。*拟议的研究将首次在实验上确定菌根互惠关系中进化的环境原因。确定这些原因将使我们能够预测互惠关系将如何演变，以应对人类对气候和资源可获得性的影响。通过测试互惠共生的力量如何影响物种共存，我们将因果地将互惠共生与维持生物多样性的过程联系起来。这项研究将有助于深入了解氮沉积的急剧增加如何影响占主导地位的互惠互利的进化和生态效应。了解这些影响很重要，因为目前在预测人为变化将如何影响生态系统功能时没有考虑到这些影响。拟议的研究将为本科生和研究生提供机会，培养在公共和私营部门进行科学研究和解决问题所需的强大的分析、项目管理和沟通技能。

Biologists seeks to explain why organisms have evolved so many different forms and functions, and to explain how this diversity influences the assembly and functioning of ecological communities. Climate and antagonistic interactions such as competition and predation have long been studied as causes of evolutionary and ecological change, but less well appreciated, though just as common, are mutualisms, in which partners exchange resources and services for mutual benefit. Nearly all organisms engage in one or more mutualisms, and it is predicted that without these interactions, the earth would support far fewer species. ******The interaction between plants and root inhabiting mycorrhizal fungi is one of the most ancient and widespread mutualisms in nature, evolving more than 400 million years ago. Nearly all plants are colonized by these fungi, who increase plant access to soil nutrients, particularly phosphorus, in exchange for sugars from photosynthesis. Though characterized as a mutualism, plant responses to fungal inoculation are quite variable, ranging from neutrality to a 100-fold stimulation of plant growth. The proposed research will experimentally test why the mutualism between plants and mycorrhizal fungi varies in nature, and how this variability affects the diversity and function of plant communities. First, we will identify the environmental factors that cause evolutionary change in the mutualism using a controlled natural selection experiment. Second, we will test whether divergence in the strength of the mutualism has consequences for population dynamics and species co-existence. Third, we will test whether widespread deposition of nitrogen from human activities, which creates acute phosphorus limitation, causes plant populations to evolve a stronger mutualism with mycorrhizal fungi, and then test whether this evolution influences nutrient cycling.******The proposed research will be the first to experimentally identify the environmental causes of evolution in the mycorrhizal mutualism. Identifying these causes will enable us to predict how mutualisms will evolve in response to anthropogenic effects on climate and resource availability. By testing how the strength of a mutualism influences species co-existence, we will causally link mutualism with processes that maintain biodiversity. The research will contribute key insights into how dramatic increases in nitrogen deposition influence the evolution and ecological effects of a dominant mutualism. Knowledge of these effects is important because they are not presently considered in forecasts of how anthropogenic change will affect ecosystem function. The proposed research will provide undergraduate and graduate students with opportunities to develop strong analytical, project management and communication skills required for both scientific research and problem solving in the public and private sector.