DISSERTATION RESEARCH: Assessing multiple mechanisms of belowground enemy release for an invasive dune-building grass species

了解入侵的潜在原因对于最大限度地减少其负面影响至关重要。当非本地植物从控制其生长的天敌中逃脱时，它们可能会成为入侵植物，这被称为敌人释放假说。这些植物的天敌既存在于地上，也存在于地下，尽管对地下的天敌的研究通常较少。植物寄生线虫生活在土壤中，以植物根系为食，可以控制原生植物的生长。然而，关于线虫的进食偏好，以及入侵植物是否因这些偏好而逃脱伤害，人们知之甚少。此外，植物寄生线虫有多种不同的摄食策略。有些有在根表面取食的一般策略，而另一些则有更专门的方法，在根组织中挖洞，在根内取食。这些取食策略的差异可能会影响入侵植物在入侵新地区时释放敌人的强度。本研究将为研究入侵植物及其躲避天敌提供新的思路，同时为EPSCoR状态下的本科生提供宝贵的研究机会。由于本研究的重点是五大湖沙丘中的入侵草，本研究将有助于更好地了解五大湖沿海生态和管理。该项目旨在了解与敌人释放相关的两个因素-植物寄生线虫的摄食偏好和植物对通才和专一敌人释放的生长反应。以沙黑麦草（Leymus arenarius）入侵以美国滩草（amophila breviligulata）为主的沙丘为模型系统，本研究将解决两个基本问题：植物寄生线虫是否表现出对本地植物比非本地植物更偏好的食性？非本地植物从专门食草动物身上获得的释放比从通才食草动物身上获得的释放更大吗？这些问题将通过一系列的实验室和温室实验得到解答。这些结果将揭示线虫是否可以探测到植物的根，是否表现出对某些植物的偏好，以及这些偏好是否随着摄食专业化而变化。在一个配套的温室实验中，将评估植物对线虫取食专业化和密度的反应。本研究结果将拓宽对地下食草动物在外来植物入侵过程中释放天敌作用的认识。

Understanding the reasons underlying invasion is critical for minimizing their negative impacts. Non-native plants may become invasive when they escape their natural enemies that control their growth in their native range, which is called the enemy release hypothesis. These natural enemies of plants occur both above- and belowground, though belowground enemies have generally been less well studied. Plant-parasitic nematodes live in soil, feed on plant roots, and can control the growth of native plants. However, little is known about feeding preferences of nematodes, and whether invasive plants escape damage due to these preferences. Additionally, plant-parasitic nematodes have a variety of different feeding strategies. Some have a general strategy of feeding on the root surface, while others have a more specialized approach of burrowing into the root tissue to feed inside the root. Differences in these feeding strategies may affect the strength of enemy release that invasive plants experience when they invade into new areas. This research will provide insights into invasive plants and their escape from natural enemies while providing valuable research opportunities to undergraduate students in an EPSCoR state. Because this work focuses on an invasive grass in the Great Lakes sand dunes, this work will contribute to a better understanding of Great Lakes coastal ecology and management. This project seeks to understand two factors related to enemy release - feeding preferences of plant-parasitic nematodes and plant growth responses to release from generalist and specialized enemies. Using invasion by Leymus arenarius (sand ryegrass) into Ammophila breviligulata (American beachgrass) dominated sand dunes as a model system, this research will address two basic questions: Do plant-parasitic nematodes exhibit feeding preferences for native plants over non-native plants? Do non-native plants experience greater release from specialist herbivores over generalist herbivores? These questions will be answered using a series of lab and greenhouse experiments. These results will reveal whether nematodes can detect plant roots, exhibit preferences for certain plants, and whether these preferences vary with feeding specialization. In a companion greenhouse experiment, plant responses to nematode feeding specialization and density will be assessed. Results from this work will broaden the understanding of the role belowground herbivores play in enemy release during non-native plant invasion.