McCary Matthew A, Zellner Moira, Wise David H
Department of Biological Sciences University of Illinois Chicago Illinois.
Institute for Environmental Science and Policy University of Illinois Chicago Illinois.
Ecol Evol. 2019 Jan 28;9(4):2018-2030. doi: 10.1002/ece3.4892. eCollection 2019 Feb.
Understanding the factors that determine invasion success for non-native plants is crucial for maintaining global biodiversity and ecosystem functioning. One hypothesized mechanism by which many exotic plants can become invasive is through the disruption of key plant-mycorrhizal mutualisms, yet few studies have investigated how these disruptions can lead to invader success. We present an individual-based model to examine how mutualism strengths between a native plant () and mycorrhizal fungus can influence invasion success for a widespread plant invader, (garlic mustard). Two questions were investigated as follows: (a) How does the strength of the mutualism between the native and a mycorrhizal fungus affect resistance (i.e., native plant maintaining >60% of final equilibrium plant density) to garlic mustard invasion? (b) Is there a non-linear relationship between initial garlic mustard density and invasiveness (i.e., garlic mustard representing >60% of final equilibrium plant density)? Our findings indicate that either low (i.e., facultative) or high (i.e., obligate) mutualism strengths between the native plant and mycorrhizal fungus were more likely to lead to garlic mustard invasiveness than intermediate levels, which resulted in higher resistance to garlic mustard invasion. Intermediate mutualism strengths allowed to take advantage of increased fitness when the fungus was present but remained competitive enough to sustain high numbers without the fungus. Though strong mutualisms had the highest fitness without the invader, they proved most susceptible to invasion because the loss of the mycorrhizal fungus resulted in a reproductive output too low to compete with garlic mustard. Weak mutualisms were more competitive than strong mutualisms but still led to garlic mustard invasion. Furthermore, we found that under intermediate mutualism strengths, the initial density of garlic mustard (as a proxy for different levels of plant invasion) did not influence its invasion success, as high initial densities of garlic mustard did not lead to it becoming dominant. Our results indicate that plants that form weak or strong mutualisms with mycorrhizal fungi are most vulnerable to invasion, whereas intermediate mutualisms provide the highest resistance to an allelopathic invader.
了解决定非本地植物入侵成功的因素对于维护全球生物多样性和生态系统功能至关重要。许多外来植物能够成为入侵物种的一种假设机制是通过破坏关键的植物与菌根共生关系，但很少有研究调查这些破坏如何导致入侵者成功。我们提出了一个基于个体的模型，以研究本地植物（）与菌根真菌之间的共生强度如何影响一种广泛分布的植物入侵者——大蒜芥（）的入侵成功。研究了以下两个问题：（a）本地植物与菌根真菌之间的共生强度如何影响对大蒜芥入侵的抗性（即本地植物维持最终平衡植物密度的>60%）？（b）初始大蒜芥密度与入侵性（即大蒜芥占最终平衡植物密度的>60%）之间是否存在非线性关系？我们的研究结果表明，本地植物与菌根真菌之间低（即兼性）或高（即专性）的共生强度比中等水平更有可能导致大蒜芥的入侵性，中等水平导致对大蒜芥入侵的更高抗性。中等共生强度使在有真菌存在时能够利用增加的适合度，但在没有真菌时仍具有足够的竞争力以维持高数量。虽然在没有入侵者的情况下强共生关系具有最高的适合度，但它们被证明最容易受到入侵，因为菌根真菌的丧失导致繁殖产量过低，无法与大蒜芥竞争。弱共生关系比强共生关系更具竞争力，但仍然导致大蒜芥入侵。此外，我们发现，在中等共生强度下，大蒜芥的初始密度（作为不同植物入侵水平的代表）不影响其入侵成功，因为高初始密度的大蒜芥不会导致其成为优势种。我们的结果表明，与菌根真菌形成弱或强共生关系的植物最容易受到入侵，而中等共生关系对化感入侵者提供最高抗性。
