Data from: Quantifying the effects of ecological constraints on trait expression using novel trait-gradient analysis parameters

1. Complex processes related to biotic and abiotic forces can impose limitations to assembly and composition of plant communities. Quantifying the effects of these constraints on plant functional traits across environmental gradients, and among communities, remains challenging. We define ecological constraint (Ci) as the combined, limiting effect of biotic interactions and environmental filtering on trait expression (i.e., the mean value and range of functional traits). 2. Here we propose a set of novel parameters to quantify this constraint by extending the trait-gradient analysis (TGA) methodology. The key parameter is ecological constraint, which is dimensionless and can be measured at various scales, e.g., on population and community levels. It facilitates comparing the effects of ecological constraints on trait expressions across environmental gradients, as well as within and among communities. 3. We illustrate the implementation of the proposed parameters using the bark thickness of 14 woody species along an aridity gradient on granite outcrops in southwestern Australia. We found a positive correlation between increasing environmental stress and strength of ecological constraint on bark thickness expression. Also, plants from more stressful habitats (shrublands on shallow soils and in sun-exposed locations) displayed higher ecological constraint for bark thickness than plants in more benign habitats (woodlands on deep soils and in sheltered locations). 4. The relative ease of calculation and dimensionless nature of Ci allow it to be readily implemented at various scales and make it widely applicable. It therefore has the potential to advance the mechanistic understanding of the ecological processes shaping trait expression. Some future applications of the new parameters could be investigating the patterns of ecological constraints i) among communities from different regions, ii) on different traits across similar environmental gradients, and iii) for the same trait across different gradient-types.,Ottaviani et al 2017_Ecol Evol_bark thickness dataBark thickness data were collected in the field for 14 plant species, from seven granite outcrops across an aridity gradient in Southwestern Australia, in 2012. In each study site, 3-4 species were sampled. For each species 10 individuals were sampled (in each outcrop). For each plant sampled, 5 different bark thickness measurements were collected, then averaged.,

1. 生物与非生物因子相关的复杂过程，会对植物群落的组装与组成造成限制。量化这些约束因子沿环境梯度、在不同群落间对植物功能性状（functional traits）的影响，仍是一项具有挑战性的工作。本研究将生态约束（ecological constraint，Ci）定义为生物交互作用与环境过滤对性状表达（即功能性状的均值与分布范围）的综合限制效应。
2. 本研究通过拓展性状梯度分析（trait-gradient analysis，TGA）方法，提出了一套用于量化该约束的全新参数体系。其中核心参数为生态约束，该参数无量纲，可在多个尺度上进行测算，例如种群与群落水平。该参数有助于比较沿环境梯度、以及群落内部和不同群落间，生态约束对性状表达的影响强度。
3. 我们以澳大利亚西南部花岗岩露头干旱梯度上14种木本植物的树皮厚度为例，展示了所提参数的应用流程。研究发现，环境胁迫的增强与树皮厚度相关生态约束强度呈正相关关系。此外，相较于生境更温和的植物（分布于深土林地、遮阴环境），来自胁迫更强生境的植物（分布于浅土灌丛、向阳环境），其树皮厚度的生态约束程度更高。
4. 生态约束Ci的计算相对简便且无量纲，使其可便捷地应用于多种尺度，具备广泛的适用性。因此，该参数体系有望推动学界对塑造性状表达的生态过程的机制性理解。该新型参数体系的未来应用方向可包括：i）探究不同区域群落间的生态约束格局；ii）在相似环境梯度下分析不同性状的生态约束模式；iii）在不同梯度类型下分析同一性状的生态约束模式。

Ottaviani等（2017）发表于《Ecol Evol》的树皮厚度数据集
该数据集于2012年在澳大利亚西南部沿干旱梯度的7处花岗岩露头中，采集了14种植物的野外树皮厚度数据。每个研究样地内采样3-4个物种，每个物种在每个露头样地中采样10个个体。每株采样植物的树皮厚度共测量5次，随后取平均值作为该植株的树皮厚度值。