Plant diversity varies immensely over large-scale gradients in temperature, precipitation, and seasonality at global and regional scales. This relationship may be driven in part by climatic variation in the relative importance of abiotic and biotic interactions to the diversity and composition of plant communities. In particular, biotic interactions may become stronger and more host specific with increasing precipitation and temperature, resulting in greater plant species richness in wetter and warmer environments. This hypothesis predicts that the many defensive compounds found in plants’ metabolomes should increase in richness and decrease in interspecific similarity with precipitation, temperature, and plant diversity. To test this prediction, we compared patterns of chemical and morphological trait diversity of 140 woody plant species among seven temperate forests in North America representing 16.2 °C variation in mean annual temperature (MAT), 2,115 mm variation in mean annual precipitation (MAP), and from 10 to 68 co-occurring species. We used untargeted metabolomics methods based on data generated with liquid chromatography-tandem mass spectrometry to identify, classify, and compare 13,480 unique foliar metabolites and to quantify the metabolomic similarity of species in each community with respect to the whole metabolome and each of five broad classes of metabolites. In addition, we compiled morphological trait data from existing databases and field surveys for three commonly measured traits (specific leaf area [SLA], wood density, and seed mass) for comparison with foliar metabolomes. We found that chemical defense strategies and growth and allocation strategies reflected by these traits largely represented orthogonal axes of variation. In addition, functional dispersion of SLA increased with MAP, whereas functional richness of wood density and seed mass increased with MAT. In contrast, chemical similarity of co-occurring species decreased with both MAT and MAP, and metabolite richness increased with MAT. Variation in metabolite richness among communities was positively correlated with species richness, but variation in mean chemical similarity was not. Our results are consistent with the hypothesis that plant metabolomes play a more important role in community assembly in wetter and warmer climates, even at temperate latitudes, and suggest that metabolomic traits can provide unique insight to studies of trait-based community assembly.

中文翻译：

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在北美森林中，共生树木的化学相似性随降水和温度的降低而降低

在全球和区域范围内，植物的多样性在温度，降水和季节的大规模梯度上变化很大。这种关系可能部分是由于非生物和生物相互作用对植物群落多样性和组成的相对重要性的气候变化所驱动。特别是，随着降水和温度的升高，生物相互作用可能会变得更强，并且更具宿主特异性，从而导致在潮湿和温暖的环境中植物物种更加丰富。该假设预测，植物代谢组中发现的许多防御性化合物应随着降水，温度和植物多样性而增加其丰富度，并降低种间相似性。为了检验这个预测，我们比较了北美7个温带森林中140种木本植物物种的化学和形态性状多样性模式，这些模式分别表示年均温度（MAT），平均年降水量（MAP），1,115 mm和10至68之间的变化为16.2°C共生物种。我们使用了基于液相色谱-串联质谱法生成的数据的非靶向代谢组学方法，以识别，分类和比较13480种独特的叶状代谢产物，并就整个代谢组和五大类中的每一个量化每个群落中物种的代谢组学相似性代谢产物。此外，我们从现有数据库和田间调查中收集了三个常用测量特征（特定叶面积[SLA]，木材密度，和种子质量）与叶代谢组进行比较。我们发现这些特征所反映的化学防御策略以及生长和分配策略在很大程度上代表了变异的正交轴。此外，SLA的功能分散性随MAP的增加而增加，而木材密度和种子质量的功能丰富度随MAT的增加而增加。相反，同时存在的物种的化学相似性随MAT和MAP降低，而代谢产物丰富度随MAT升高。群落之间代谢物丰富度的变化与物种丰富度呈正相关，但平均化学相似度的变化却没有。我们的结果与以下假设相吻合：在潮湿和温暖的气候下，即使在温带地区，植物代谢组在群落组装中也起着更重要的作用，