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的数量。例如，以食草动物为食的捕食者可以通过直接消耗食草动物或通过所谓的“非消耗效应”间接减少食草动物对植物群落的压力。非消耗效应通常发生在捕食者的存在导致被捕食物种减少进食活动以避免被吃掉时。这种反捕食者行为对食草动物的生存有重要影响，也可能对那些可能被食草动物吃掉的植物有重要影响。这种对植物的影响由于许多捕食者是杂食性的，既吃植物也吃动物而变得更加复杂。该项目研究了以种子为食的地甲虫和既吃种子又吃地甲虫的老鼠如何相互影响，并影响一种它们吃掉种子的常见植物（羊蹄）的丰度。由于羔羊是一种重要的农业杂草，本研究的结果对农民的杂草管理有直接的影响。该项目将为一名研究生提供跨学科培训，并将包括一名本科生研究员的指导。该项目的概念和结果将被纳入普渡大学的教学课程，并将在科学会议以及以农民为重点的农业会议上发表。这些作品还将在各种外联活动中向公众进行解释，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，这个项目将使用一个种子捕食者食物网来研究在多个营养水平上驱动复杂的捕食者-猎物相互作用的环境和行为因素。初步数据表明，啮齿动物利用捕食者介导的避难所干扰了甲虫的活动和种子的清除。在小鼠存在的情况下，甲虫去除种子的减少可归因于公会内捕食（消耗效应）或反捕食者警惕（非消耗效应；NCEs）。这两种不同但非互斥的营养途径对植物种群动态有不同的长期影响。本项目将以这些概念为基础，对种子觅食者对捕食风险的反应进行实验。它将解决三个具体问题：1)种子捕食是否受到公会内捕食者nce的影响？2)结构性避难所是否调解nce对种子捕食的影响？3)避难生境是否影响脊椎动物/无脊椎动物捕食事件的频率？该实验将研究食肉动物的存在和保护覆盖物的可用性如何影响食草动物对羔羊窝种子的觅食行为。

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.