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理解环境变化如何以及为什么会影响物种的相互作用。食物网描述了生物之间的摄食关系，说明了植物和动物在自然群落中的生态作用。食物网也描述了整个摄食互动是如何运作的。了解不同地方的食物网如何以及为什么不同是很重要的，因为它可以帮助预测环境变化的生态影响，比如物种损失或栖息地变化。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。研究重点是植物与毛虫、毛虫与天敌之间的取食相互作用。通过记录北加州低肥力和高肥力土壤中的“谁吃谁”，该项目将能够描述复杂的食物网，并询问这些网络在不同土壤类型中是如何不同的。由于我们对这一主题的大部分理解来自受肥料影响的土壤的农业生态系统，该项目将提供新的见解，因为它基于自然变化的土壤肥力。这项研究将涉及几个本科生和一个生态学俱乐部。土壤资源变异是一种普遍存在的环境异质性形式，对生物性状和物种相互作用具有强烈的直接和间接影响。多种理论解释了资源水平对营养相互作用的影响：资源可得性假说（resource Availability Hypothesis， RAH）认为资源可得性塑造了植物性状，从而影响了它们对食草动物的质量；反过来，慢生长高死亡率假说（SGHM）和高性能高死亡率假说（HPHM）将植物质量与食草动物和天敌之间的相互作用联系起来。基于这些理论，本研究将厘清在形成植物-毛虫-顶部捕食者三营养相互作用中，捕食和营养及防御性状的相互作用。利用加利福尼亚低肥力蛇形和高肥力非蛇形土壤的天然马赛克，该项目将建造隔离笼，以评估顶部捕食者如何影响不同土壤类型的植物-毛毛虫相互作用。植物营养性状和防御性状将同时测量，以解开性状和捕食在不同资源背景下驱动食物网结构中的相对重要性。总之，这些实验将促进我们对物种相互作用如何以及为什么在异质景观中变化的理解。

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.