Herbivores play a critical role in plant invasions either by facilitating or inhibiting species establishment and spread. However, relatively few studies with invasive plant species have focused on the role of plant tolerance and how it varies geographically to influence invasion success. We conducted a common garden study using two lineages (native and invasive) of the grass Phragmites australis that are prevalent in North American wetlands. Using 31 populations collected across a broad geographic range, we tested five predictions: 1) the invasive lineage is more tolerant to simulated folivory than the native lineage, 2) tolerance to herbivory decreases with increasing latitude of origin of the populations, 3) estimates of tolerance are correlated with putative tolerance traits and plasticity in those traits, 4) a tradeoff exists between tolerance and resistance to herbivory and 5) tolerance has a fitness cost. Response to folivory varied substantially among populations of P. australis, ranging from intolerance to overcompensation. Our model selection procedure deemed lineage to be an important predictor of tolerance but, contrary to our prediction, the native lineage was 19% more tolerant to folivory than the invasive lineage. Tolerance for both lineages exhibited a u‐shaped relationship with latitude. A tolerance–resistance tradeoff was evident within the invasive but not the native lineage. Also, tolerance was positively correlated with belowground biomass allocation, leaf silica concentrations, specific leaf area and plasticity in stem density, and negatively correlated with the relative growth rate of the population and plasticity in putative resistance traits. Lastly, although we did not detect costs of tolerance, our results highlight that fast growth rates can maintain high fitness in the presence of herbivory. Herbivory and plant defense strategies for P. australis lineages in North America exhibit complex biogeographic patterns that cause substantial heterogeneity in enemy release and biotic resistance and, consequently, invasion success.

中文翻译：

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芦苇对草食动物的耐受性的谱系和纬度变化：对入侵成功的影响

草食动物通过促进或抑制物种的建立和传播而在植物入侵中发挥关键作用。但是，关于入侵植物物种的研究相对较少，主要集中在植物耐受性的作用及其在地理上如何影响入侵成功的方面。我们使用草芦苇的两个谱系（原生和入侵）进行了普通的花园研究在北美湿地中很普遍 在广泛的地理范围内收集了31个种群，我们测试了五个预测：1）入侵谱系比原生谱系对模拟叶面的耐受性更高； 2）对草食性的耐受性随种群起源纬度的增加而降低； 3）对种群的估计耐受性与推定的耐受性特征和这些特征中的可塑性相关，4）耐受性与对草食动物的抗性之间存在折衷，5）耐受性具有适应性成本。在澳大利亚南方人群中，对叶面的反应差异很大，范围从不宽容到过度补偿。我们的模型选择程序认为血统是耐受性的重要预测因素，但与我们的预测相反，天然血统对叶食的耐受性比侵入性血统高19％。两种血统的容忍度都表现出与纬度呈au型关系。耐受性-抵抗性折衷在浸润中很明显，但在天然谱系中却没有。同样，耐受性与地下生物量分配，叶片二氧化硅浓度，比叶面积和茎密度的可塑性正相关，而与种群的相对生长率和可逆性状的可塑性负相关。最后，尽管我们没有发现耐受性的代价，但我们的结果表明，在草食动物存在的情况下，快速的生长速度可以保持较高的适应性。北美的澳大利亚疟原虫谱系表现出复杂的生物地理格局，导致敌人释放和生物抵抗力的实质异质性，因此入侵成功。