It seems intuitive that species diversity promotes functional diversity. For example, more plant species imply more diverse leaf chemistry and thus more kinds of food for herbivores. Here we argue that the evolution of functional trait variance challenges this view. We show that trait-based eco-evolutionary processes force species to evolve narrower trait breadths in tightly packed communities, in their effort to avoid competition with neighboring species. This effect is so strong as to reduce overall trait space coverage, overhauling the expected positive relationship between species- and functional diversity. Empirical data from Galápagos land snail communities proved consistent with this claim. As a consequence, trait data from species-poor communities may misjudge functional diversity in species-rich ones, and vice versa.

中文翻译：

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性状变异的演变在物种多样性和功能多样性之间产生了张力

物种多样性促进功能多样性似乎是直觉的。例如，更多的植物物种意味着更多的叶片化学组成，因此意味着更多的食草动物食物。在这里，我们认为功能性状差异的演变挑战了这一观点。我们表明，基于特征的生态进化过程迫使物种在拥挤的社区中进化出较窄的特征宽度，从而努力避免与邻近物种竞争。这种影响是如此之强，以至于减少了整个性状空间的覆盖范围，彻底改变了物种与功能多样性之间预期的正向关系。来自加拉帕戈斯群岛蜗牛群落的经验数据证明与这一主张是一致的。结果，来自物种贫乏社区的特征数据可能会误判物种丰富社区的功能多样性，反之亦然。