In contrast to understanding spinescence in savanna woody species, little is known about the functions of plant secondary metabolites (PSM). Negative effects of PSMs on individual animal performance potentially translate into negative effects on herbivore population growth. Hence, understanding PSM functions is important for the conservation of savanna megafauna. We tested the view that black rhinoceros (Diceros bicornis) diet preference is not affected by spinescence or total phenolic abundance. We hypothesized that the composition of phenolic mixtures, however, would affect preference. Furthermore, we tested our data from 71 woody species for a trade-off between structural and chemical defenses. Spinescence type, and spinescence generally, did not deter black rhino feeding. Using eco-metabolomic data, we found that total abundance of phenolics did not affect preference, but mixture composition did and that the probability of spinescence trading off against phenolics depended on the mixture. We note that our study was restricted to black rhino and that diet preferences of other mammal herbivores might be influenced by subtle differences in phenolic mixtures. However, our results did support a previous, more detailed study of phenolic profiles of six species showing the same patterns in relation to preference generalised across mammal herbivore species in savannas. Our results represent substantial advancement in the understanding of the roles of PSMs, especially flavonoid compounds, in the functioning of savanna ecosystems, and highlight the need to dig deeper into broad groups of traits such as spinescence or total phenolics to improve understanding of woody plant defenses in savannas.

与了解稀树草原木本植物中的多刺现象相反，对植物次生代谢产物（PSM）的功能知之甚少。PSM对动物个体行为的负面影响可能转化为对草食动物种群生长的负面影响。因此，了解PSM功能对于保护热带稀树草原很重要。我们测试了黑犀牛（Diceros bicornis）饮食喜好不受刺痛或总酚含量的影响。我们假设酚类混合物的组成会影响偏好。此外，我们测试了71种木本植物的数据，以在结构防御和化学防御之间进行权衡。刺escence类型（通常为刺spin）并不能阻止黑犀牛的觅食。使用生态代谢组学数据，我们发现酚类化合物的总丰度不会影响偏爱性，但是混合物的组成会影响偏好性，并且旋光性与酚类化合物折衷的可能性取决于混合物。我们注意到，我们的研究仅限于黑犀牛，其他哺乳动物食草动物的饮食偏好可能会受到酚类混合物细微差异的影响。但是，我们的结果确实支持以前的方法，对六个物种的酚类特征进行更详细的研究，结果显示在热带稀树草原哺乳动物食草动物物种中普遍存在与偏好有关的相同模式。我们的结果代表了对PSM（尤其是类黄酮化合物）在热带稀树草原生态系统功能中的作用的理解方面的实质性进步，并强调有必要更深入地研究各种特征，例如刺花或总酚类，以增进对木本植物防御的理解在大草原。