Ecology and evolution of the mycorrhizal mutualism in a changing environment

生物学家试图解释为什么生物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运作。长期以来，气候和竞争和捕食等对抗性相互作用一直被认为是进化和生态变化的原因，但互利共生（尽管同样常见）却很少受到人们的重视，即合作伙伴为了互惠互利而交换资源和服务。几乎所有生物体都参与一种或多种互利共生，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。 ******植物与根部菌根真菌之间的相互作用是自然界中最古老、最广泛的互利共生之一，其演化历史已超过 4 亿年。几乎所有植物都被这些真菌定殖，它们增加了植物对土壤养分（尤其是磷）的获取，以换取光合作用中的糖。虽然植物对真菌接种的反应是互利共生的，但其反应却相当多变，从中性到对植物生长的 100 倍刺激。拟议的研究将通过实验测试为什么植物和菌根真菌之间的互利共生在自然界中存在差异，以及这种差异如何影响植物群落的多样性和功能。首先，我们将通过受控自然选择实验来确定导致互利共生进化变化的环境因素。其次，我们将测试互利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造成的氮的广泛沉积，造成严重的磷限制，是否导致植物种群与菌根真菌进化出更强的互利共生，然后测试这种进化是否影响养分循环。******本研究将是第一个通过实验确定菌根互利共生进化的环境原因的研究。确定这些原因将使我们能够预测互利共生将如何演变，以应对人为对气候和资源可用性的影响。通过测试互利共生的强度如何影响物种共存，我们将把互利共生与维持生物多样性的过程因果联系起来。该研究将为氮沉降的急剧增加如何影响主导互利共生的进化和生态效应提供重要见解。了解这些影响非常重要，因为目前在预测人为变化将如何影响生态系统功能时并未考虑这些影响。拟议的研究将为本科生和研究生提供机会，培养公共和私营部门科学研究和解决问题所需的强大分析、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.