Dissertation Research: Examining Anti-predator Cascades Over Four Trophic Levels

捕食者可以以复杂的方式影响猎物种群。例如，捕食草食动物的捕食者可以通过直接消耗草食动物或间接通过所谓的“非消耗效应”来减少草食动物对植物群落的压力。当捕食者的存在仅仅导致被捕食物种为了避免被吃掉而减少取食活动时，通常就会出现非消耗性效应。这种反捕食者的行为对食草动物的生存有重要影响，而且很可能对原本会被食草动物吃掉的植物产生影响。许多捕食性动物是杂食性的，既吃植物又吃动物，这一事实使对植物的这种影响变得更加复杂。这个项目研究了吃种子的地面甲虫和同时吃种子和地面甲虫的老鼠是如何相互影响的，以及它们如何影响一种常见植物(羊肚菌)的丰度，因为它们消耗的是种子。由于羊肚菌是一种重要的农业杂草，本研究的结果对农民的杂草管理具有直接的意义。这个项目将为研究生提供跨学科的培训，并将包括本科生研究人员的指导。该项目的概念和成果正在纳入普渡大学的教学课程，并将在科学会议和以农民为重点的农业会议上发表。这项工作还将在各种推广活动中向公众解释，包括农场之旅、园艺大师课程和教育网络研讨会。更具体地说，这个项目将使用种子捕食者食物网络来研究环境和行为因素，这些因素驱动着复杂的捕食者-猎物在多个营养水平上的相互作用。初步数据表明，捕食者对啮齿动物避难所的利用干扰了甲虫的活动和种子的清除。甲虫在有老鼠的情况下清除种子的减少可以归因于行会内的捕食(消耗性效应)或反捕食者的警惕(非消耗性效应；NCEs)。这两条截然不同但不相互排斥的营养途径对植物种群动态有着不同的长期影响。这个项目将建立在这些概念的基础上，进行一项关于种子采集者对捕食风险的反应的实验。它将解决三个具体问题：1)公会内捕食者的NCEs是否影响种子捕食？2)结构性避难所是否在种子捕食性NCE中起中介作用？3)避难所栖息地是否影响脊椎动物/无脊椎动物捕食事件的频率？这项实验将研究捕食者的存在和保护覆盖物的可用性如何影响花岗石在羔羊种子上的觅食行为。

Predators can affect prey populations in complex ways. Predators that eat herbivores, for example, can reduce herbivore pressure on plant communities directly by consuming the herbivores or indirectly through what is known as "non-consumptive effects". Non-consumptive effects often occur when the mere presence of a predator causes prey species to reduce feeding activity to avoid being eaten, themselves. This anti-predator behavior has important impacts on herbivore survival and likely on the plants that would otherwise be eaten by the herbivores. Such effects on plants are further complicated by the fact that many predators are omnivorous, feeding on both plants and animals. This project examines how ground beetles, which eat seeds, and mice, which eat both seeds and ground beetles, influence each other and affect the abundance of a common plant (lambsquarters), whose seeds they consume. Because lambsquarters is a weed species of agricultural importance, results of this study have direct implications for weed management by farmers. This project will provide interdisciplinary training for a graduate student and will involve mentorship of an undergraduate researcher. Concepts and results of this project are being integrated into Purdue's teaching curriculum, and will be presented at scientific conferences, as well as at farmer-focused agricultural conferences. This work will also be interpreted for the public at various outreach events including farm tours, Master Gardener courses, and educational webinars.More specifically, this project will use a seed predator food web to examine the environmental and behavioral factors that drive complex predator-prey interactions over multiple trophic levels. Preliminary data suggest that predator-mediated use of refuge by rodents interferes with beetle activity and seed removal. Reductions in seed removal by beetles in the presence of mice could be attributed to intra-guild predation (consumptive effects) or anti-predator vigilance (non-consumptive effects; NCEs). These two distinct, but non-mutually exclusive trophic pathways have different long-term implications for plant population dynamics. This project will build on these concepts with an experiment on seed-foragers' responses to predation risk. It will address three specific questions: 1) Is seed predation affected by NCEs of intra-guild predators? 2) Do structural refuges mediate NCEs on seed predation? 3) Does refuge habitat affect the frequency of vertebrate/invertebrate predation events? The experiment will examine how granivore foraging behavior on seeds of lambsquarters is impacted by the presence of predators and the availability of protective cover.