Diversity effect on plant defenses.

Summary of results from generalized linear mixed models testing for the effects of (a) big-leaf mahogany genotypic diversity and (b) plant species diversity on mahogany chemical defenses (polyphenolics and condensed tannins in the stem and leaves). To test the effect of mahogany genotype diversity we compared genotypic monocultures and genotypic polycultures, whereas to test for a species diversity effect we compared genotypic monocultures and species polycultures. Initial models testing only for an effect of diversity are designed as “Model 0”. For models labelled “Model 1”, we tested for an effect of diversity on defenses via growth-defense trade-offs by including plant height (proxy of growth) as a covariate. Finally, for models labelled “Model 2” we tested an effect of diversity via changes in herbivory by including H. grandella attack as a covariate. F-values and associated significance levels (P) are shown, as well as degrees of freedom (as subscripts in parenthesis). Significant (PPP values are typed in bold.

本部分为广义线性混合模型（generalized linear mixed models）的结果总结，用于检验(a)大叶桃花心木（big-leaf mahogany）基因型多样性（genotypic diversity）以及(b)植物物种多样性（plant species diversity）对桃花心木化学防御物质的影响，其中防御物质指茎、叶中的多酚类与缩合单宁（condensed tannins）。为检验桃花心木基因型多样性的效应，本研究将基因型单种栽培与基因型混种栽培进行对比；而为检验物种多样性的效应，则将基因型单种栽培与物种混种栽培进行对比。仅检验多样性效应的初始模型被命名为"模型0"。对于标记为"模型1"的模型，我们通过纳入植株高度（生长的替代指标）作为协变量，检验多样性通过生长-防御权衡（growth-defense trade-offs）对防御物质产生的影响。最后，对于标记为"模型2"的模型，我们通过纳入H. grandella取食危害作为协变量，检验多样性通过植食性昆虫取食变化产生的效应。结果展示了F值及其对应的显著性水平（P值），以及自由度（以括号内下标形式呈现）。具有统计学显著性的P值以粗体标注。