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首页> 外文学位 >Influence of insect herbivory, plant competition and plant defense on the invasion success of hoary cress (Lepidium draba L. (Brassicaceae)).
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Influence of insect herbivory, plant competition and plant defense on the invasion success of hoary cress (Lepidium draba L. (Brassicaceae)).

机译：昆虫食草，植物竞争和植物防御对白菊入侵的成功的影响（Lepidium draba L.（Brassicaceae））。

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This thesis addressed two goals: to increase knowledge of the basic biological responses of the invasive mustard hoary cress, Lepidium draba, to a variety of biotic stressors, and to study the processes of clonal plant invasions in light of three invasion hypotheses: biotic resistance, enemy release, and evolution of increased competitive ability (EICA).;To test the enemy release hypotheses, I identified four oligophagous insect herbivores from the introduced range to act as surrogates for potential biological control agents to assess the impact of specific feeding niches on the target weed. I applied this novel technique to assess the role of increased generalist herbivory on hoary cress by examining the density-dependent impact of these herbivores individually and in combination. Defoliation by the diamondback moth Plutella xylostella had the strongest, most consistent impact, while the stem-mining weevil Ceutorhynchus americanus had the highest per capita effect. In multiple-species experiments, herbivore impacts were usually additive, and hoary cress tolerated high herbivore densities.;I investigated the competitive ability of hoary cress against ten Festuca and Poa grass species from North America and Europe. In both genera, Eurasian species were more competitive against L. draba than their North American congeners. Regardless of origin, sod-forming Poa species appeared more competitive against L. draba.;I compared vegetative regeneration, herbivore damage, and glucosinolate defense induction of L. draba from European and North American populations in a shared greenhouse EICA experiment. The number of root buds/cm was greater in European populations, potentially allowing better establishment in competitive environments, but no differences were observed between ranges in later stages of plant growth. Feeding rate and survival of P. xylostella also did not differ. Insect herbivory had no effects on the eight identified glucosinolates. Comparing glucosinolate profiles with those previously reported indicated that the plants may have already been in an induced defense state; therefore they were not responsive to herbivory. There were no differences in glucosinolate profiles between ranges.;I conclude that biotic resistance, enemy release, and EICA play a part in the invasion success of L. draba, but that none of these hypotheses completely explain its dominance in North America.
机译：本论文解决了两个目标：增加对芥菜入侵性芥菜Lepidium draba的基本生物学反应的认识，以及对多种生物胁迫的研究，并根据三种入侵假说研究克隆植物入侵的过程：生物抗性，敌人释放，以及增强竞争能力的进化（EICA）。为了测试敌人释放假设，我从引入的范围内鉴定了四种寡食性食草动物，作为潜在的生物防治剂的代用品，以评估特定的饲料ni对种群的影响。目标杂草。我通过研究这些食草动物单独或结合在一起对密度的影响，应用了这项新技术来评估增加的食草动物对白菊的作用。小菜蛾对小菜蛾的落叶效果最强，最一致，而挖茎象鼻美洲象鼻虫的人均效果最高。在多物种实验中，食草动物的影响通常是相加的，并且白芥子可以忍受较高的草食动物密度。我研究了白芥子对来自北美和欧洲的10种Festuca和Poa草种的竞争能力。在这两个属中，欧亚种对德拉巴乳杆菌的竞争性都比其北美同类物种更具竞争性。不论起源如何，形成草皮的Poa物种对德拉巴L.draba的竞争力都更强。我在一个共同的温室EICA实验中比较了欧洲和北美种群对德拉巴L. draba的营养再生，草食动物损害和芥子油苷防御诱导。在欧洲人口中，每厘米的根芽数更多，可能在竞争环境中更好地定植，但在植物生长后期的范围之间未观察到差异。小菜蛾的摄食率和存活率也没有差异。食草昆虫对八种芥子油苷没有影响。比较芥子油苷和先前报道的芥子油苷分布表明，植物可能已经处于诱导防御状态。因此他们对草食动物没有反应。硫代芥子油苷的分布范围之间没有差异。我得出结论，生物抗性，敌人释放和EICA参与了德拉巴乳杆菌的入侵成功，但是这些假说都不能完全解释其在北美的统治地位。

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