Department of Biology, University of Turku, Turku, Finland.
University of Bordeaux, INRAE, BIOGECO, Cestas, France.
Ecol Lett. 2024 May;27(5):e14440. doi: 10.1111/ele.14440.
Variation in herbivore pressure has often been predicted from patterns in plant traits considered as antiherbivore defences. Here, we tested whether spatial variation in field insect herbivory is associated with the variation in plant quality by conducting a meta-analysis of 223 correlation coefficients between herbivory levels and the expression of selected plant traits. We found no overall correlation between herbivory and either concentrations of plant secondary metabolites or values of physical leaf traits. This result was due to both the large number of low correlations and the opposing directions of high correlations in individual studies. Field herbivory demonstrated a significant association only with nitrogen: herbivore pressure increased with an increase in nitrogen concentration in plant tissues. Thus, our meta-analysis does not support either theoretical prediction, i.e., that plants possess high antiherbivore defences in localities with high herbivore pressure or that herbivory is low in localities where plant defences are high. We conclude that information about putative plant defences is insufficient to predict plant losses to insects in field conditions and that the only bottom-up factor shaping spatial variation in insect herbivory is plant nutritive value. Our findings stress the need to improve a theory linking plant putative defences and herbivory.
食草动物压力的变化通常可以根据被认为是抗食草动物防御的植物特征模式来预测。在这里，我们通过对 223 个食草水平与选定植物特征表达之间相关性系数的荟萃分析，检验了田间昆虫食草性的空间变化是否与植物质量的变化有关。我们发现，食草与植物次生代谢物浓度或物理叶片特征值之间没有总体相关性。这一结果归因于个别研究中大量低相关性和高相关性的相反方向。田间食草仅与氮素表现出显著的相关性，即随着植物组织中氮素浓度的增加，食草压力增大。因此，我们的荟萃分析既不支持理论预测，即植物在食草压力高的地方具有高抗食草动物防御能力，也不支持食草率低的地方植物防御能力高的理论预测。我们的结论是，关于植物防御能力的信息不足以预测植物在田间条件下遭受昆虫侵害的损失，而唯一能影响昆虫食草性空间变化的自下而上的因素是植物营养价值。我们的研究结果强调了需要改进将植物潜在防御与食草联系起来的理论。
