1. Trait diversity is traditionally seen as promoting species richness and ecosystem function. Species with dissimilar traits would partition available resources, increasing niche differences, facilitating coexistence and increasing ecosystem function.
2. Here we first show, using theory and simulations for light-limited phytoplankton, that combing photosynthetic pigments is indeed a necessary condition for coexistence and stimulates ecosystem function.
3. However, pigment richness does mostly not permit the coexistence of more than two species, and increases productivity at most 40% compared to single-pigment communities. That is because blending in more pigments leads to coexistence of species with many pigments and therefore flat absorption spectra, which equalizes their fitness but decreases their niche differences. Similarly, seeding species with more variable size leads to an excess of large-celled species, which does not only decrease fitness differences but also niche differences.
4. Empirical data and additional simulations suggest that pigment richness effects can be stronger during transient dynamics but inevitably weaken with time, that is, pigment richness effects on species richness and function are likely short-lived.
5. Synthesis. Our results highlight the need to apply coexistence theory to understand the long-term effects of trait diversity on biodiversity and ecosystem function.

中文翻译：

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色素丰富度和大小变化对光限制浮游植物共存、丰富度和功能的影响

1. 传统上，性状多样性被视为促进物种丰富度和生态系统功能。具有不同特征的物种会划分可用资源，增加生态位差异，促进共存并增加生态系统功能。
2. 在这里，我们首先利用光限制浮游植物的理论和模拟表明，结合光合色素确实是共存和刺激生态系统功能的必要条件。
3. 然而，色素丰富度大多不允许两种以上的物种共存，与单一色素群落相比，生产力最多提高 40%。这是因为混合更多色素导致物种与许多色素共存，因此吸收光谱平坦，这使它们的适应度相等，但减少了它们的生态位差异。同样，大小可变的播种物种会导致大细胞物种过多，这不仅会减少适应度差异，还会减少生态位差异。
4. 经验数据和额外的模拟表明，在瞬态动态过程中，色素丰富度的影响可能会更强，但随着时间的推移不可避免地会减弱，也就是说，色素丰富度对物种丰富度和功能的影响可能是短暂的。
5. 合成。我们的结果强调需要应用共存理论来了解性状多样性对生物多样性和生态系统功能的长期影响。