Biodiversity is defined by trait-differences between organisms, and biologists have long sought to predict associations among ecologically important traits: why do some traits trade off while others are co-expressed? Why might some trait associations hold across levels of organization, from individuals and genotypes to populations and species, while others only occur at one level? Understanding such scaling is a core biological problem, bearing on the evolution of ecological strategies as well as forecasting responses to environmental change. Explicitly considering the hierarchy of biodiversity and expectations at each scale (individual change, evolution within and among populations, and species turn-over) is necessary as we work towards a predictive framework in evolutionary ecology. Within species, a trait may have an association with another trait due to phenotypic plasticity, genetic correlation, or population-level local adaptation. Plastic responses are often adaptive and yet individuals have a fixed pool of resources; thus, positive and negative trait associations can be generated by immediate environmental needs and energetic demands. Genetic variation and covariation for traits within a population are typically shaped by varying natural selection in space and time. Although genetic correlations are infrequently long-term constraints, they may indicate competing organismal demands. Traits are often quantitatively differentiated (local adaptation) among populations, although selection rarely favors qualitatively different strategies until populations become reproductively isolated. Across species, niche specialization to particular habitats or biotic interactions may determine trait correlations, a subset of which are termed "strategic trade-offs" because they are a consequence of adaptive specialization. Across scales, constraints within species often do not apply as new species evolve, and conversely, trait correlations observed across populations or species may not be reflected within populations. I give examples of such scale-dependent trait associations and their causes across taxonomic groups and ecosystems, and in the final section of the paper I specifically evaluate leaf economic spectrum traits and their associations with plant defense against herbivory. Scale-dependent predictions emerge for understanding plant ecology holistically, and this approach can be fruitfully applied more generally in evolutionary ecology. Adaptive specialization and community context are two of the primary drivers of trade-offs and syndromes across biological scales.

中文翻译：

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生物生物学中权衡、综合征和专业化的尺度依赖框架

生物多样性是由生物体之间的性状差异定义的，生物学家长期以来一直试图预测生态重要性状之间的关联：为什么有些性状会相互抵消而另一些性状是共同表达的？为什么有些性状关联可以跨越组织层次，从个体和基因型到种群和物种，而另一些则只发生在一个层次上？了解这种尺度是一个核心生物学问题，关系到生态战略的演变以及预测对环境变化的反应。当我们致力于进化生态学的预测框架时，有必要明确考虑每个尺度（个体变化、种群内部和种群之间的进化以及物种更替）的生物多样性等级和期望。在物种内，由于表型可塑性、遗传相关性或种群水平的局部适应性，一个性状可能与另一个性状相关联。可塑性反应通常是适应性的，但个人拥有固定的资源池；因此，直接的环境需求和能量需求可以产生积极和消极的特征关联。种群内性状的遗传变异和协变通常是由空间和时间上不同的自然选择形成的。尽管遗传相关性很少是长期的限制因素，但它们可能表明存在竞争性的有机体需求。种群之间的特征通常在数量上有所不同（局部适应），尽管在种群变得生殖隔离之前，选择很少有利于质量不同的策略。跨物种，特定栖息地或生物相互作用的利基专业化可能决定性状相关性，其中的一个子集被称为“战略权衡”，因为它们是适应性专业化的结果。在跨尺度上，物种内的约束通常不会随着新物种的进化而适用，相反，跨种群或物种观察到的性状相关性可能不会在种群内反映出来。我举例说明了这种与尺度相关的性状关联及其跨分类群和生态系统的原因，在论文的最后一部分，我专门评估了叶片经济谱性状及其与植物防御食草性的关联。出现了依赖尺度的预测来全面理解植物生态学，这种方法可以更广泛地应用于进化生态学。