Plants produce an enormous diversity of secondary metabolites, but the evolutionary mechanisms that maintain this diversity are still unclear. The interaction diversity hypothesis suggests that complex chemical phenotypes are maintained because different metabolites benefit plants in different pairwise interactions with a diversity of other organisms. In this synthesis, we extend the interaction diversity hypothesis to consider that fruits, as potential hotspots of interactions with both antagonists and mutualists, are likely important incubators of phytochemical diversity. We provide a case study focused on the Neotropical shrub Piper reticulatum that demonstrates: 1) secondary metabolites in fruits have complex and cascading effects for shaping the outcome of both mutualistic and antagonistic fruit–frugivore interactions, and; 2) fruits can harbor substantially higher levels of phytochemical diversity than leaves, even though leaves have been the primary focus of plant chemical ecology research for decades. We then suggest a number of research priorities for integrating chemical ecology with fruit–frugivore interaction research and make specific, testable predictions for patterns that should emerge if fruit interaction diversity has helped shape phytochemical diversity. Testing these predictions in a range of systems will provide new insight into the mechanisms driving frugivory and seed dispersal and shape an improved, whole-plant perspective on plant chemical trait evolution.

中文翻译：

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水果、食果动物和植物化学多样性的演变

植物产生的次生代谢物种类繁多，但维持这种多样性的进化机制仍不清楚。相互作用多样性假设表明，复杂的化学表型得以维持，因为不同的代谢物在与其他生物多样性的不同成对相互作用中有益于植物。在这个综合中，我们扩展了相互作用多样性假设，认为水果作为与拮抗剂和互惠互利者相互作用的潜在热点，可能是植物化学多样性的重要孵化器。我们提供了一个专注于新热带灌木Piper reticulatum的案例研究这表明：1) 水果中的次生代谢物具有复杂的级联效应，可塑造互惠和拮抗的水果-食果动物相互作用的结果，以及；2) 水果的植物化学多样性比叶子的含量要高得多，尽管叶子几十年来一直是植物化学生态学研究的主要焦点。然后，我们提出了一些将化学生态学与水果-食果动物相互作用研究结合起来的研究重点，并对水果相互作用多样性有助于塑造植物化学多样性时应该出现的模式做出具体的、可测试的预测。在一系列系统中测试这些预测将为推动食果和种子传播的机制提供新的见解，并形成一个改进的、全植物视角的植物化学性状进化。