DISSERTATION RESEARCH: Soil resource variability as a driver of interactions within, and emergent properties of, tritrophic ecological networks

生态学的一个关键目标是了解环境变化如何以及为什么会影响物种之间的相互作用。食物网描述了生物体之间的摄食关系，并说明了植物和动物在自然群落中的生态作用。食物网还描述了整个摄食相互作用的运作方式。了解不同地方的食物网如何以及为什么不同很重要，因为它可以帮助预测环境变化的生态影响，如物种丧失或栖息地变化。在这个项目中，研究人员将研究土壤养分的变化如何导致食物网的差异。研究的重点是植物与毛虫、毛虫与捕食者之间的取食相互作用。通过记录北加州低肥力土壤和高肥力土壤中的“谁吃谁”，这个项目将能够描述复杂的食物网，并询问这些网在不同土壤类型中有何不同。由于我们对这一主题的大部分理解来自于土壤受到化肥影响的农业生态系统，因此该项目将提供新的见解，因为它基于自然肥力不同的土壤。这项研究将包括几名本科生和一个生态俱乐部。土壤资源的变异是环境异质性的一种普遍形式，对生物性状和物种间的相互作用有很强的直接和间接影响。多种理论阐述了资源水平对营养相互作用的影响：资源可用性假说(RAH)认为，资源的可用性应该塑造植物的性状，从而决定它们对食草动物的品质；反过来，慢生长、高死亡率(SGHM)和高性能、高死亡率假说(HPHM)将植物品质与草食动物和天敌之间的相互作用联系起来。基于这些理论，本研究将解开捕食与营养和防御植物性状在形成植物-毛虫-顶部捕食者三营养相互作用中的交互作用。利用加州低肥力的蛇纹土和高肥力的非蛇纹土的天然马赛克，该项目将建造排除笼子，以评估顶部捕食者如何影响不同土壤类型的植物-毛虫相互作用。将同时测量植物的营养和防御特性，以弄清特性和捕食在推动不同资源背景下的食物网络结构方面的相对重要性。总而言之，这些实验将促进我们对物种相互作用如何以及为什么在不同的景观中变化的理解。

A key goal in ecology is understanding how and why environmental variation shapes species interactions. Food webs describe the feeding relationships between organisms, and illustrate the ecological roles of plants and animals in natural communities. Food webs also describe how the entire suite of feeding interactions might function. Understanding how and why food webs differ between places is important because it can help predict ecological impacts of environmental change such as species loss or habitat change. In this project, researchers will study how changes in soil nutrients cause differences in food webs. The research focuses on the feeding interactions between plants and caterpillars, and between caterpillars and their predators. By documenting "who eats whom" in Northern California soils of low versus high fertility, this project will be able to describe complex food webs and ask how these webs are different across soil types. Because most of our understanding of this topic comes from agricultural ecosystems that have soils impacted by fertilizer, this project will provide new insights as it is based on soils that naturally vary in fertility. This research will involve several undergraduate students and an ecology club. Variation in soil resources is a ubiquitous form of environmental heterogeneity, with strong direct and indirect effects on organismal traits and species interactions. Multiple theories address the effects of resource level on trophic interactions: the Resource Availability Hypothesis (RAH) suggests that resource availability should shape plant traits and, consequently, their quality to herbivores; in turn, the Slow Growth, High Mortality (SGHM) and High Performance, High Mortality Hypotheses (HPHM) relate plant quality to interactions between herbivores and natural enemies. Based on these theories, this research will disentangle the interacting roles of predation and nutritive and defensive plant traits in shaping plant-caterpillar-top predator tri-trophic interactions. Using a natural mosaic of low fertility serpentine and higher fertility non-serpentine soils in California, this project will build exclusion cages to assess how top-predators affect plant-caterpillar interactions across different soil types. Plant nutritive and defensive traits will be measured simultaneously to disentangle the relative importance of traits and predation in driving food web structure across different resource contexts. Together, these experiments will advance our understanding of how and why species interactions vary across heterogeneous landscapes.