Ottaviani Gianluigi, Tsakalos James L, Keppel Gunnar, Mucina Ladislav
School of Biological Sciences The University of Western Australia Perth WA Australia.
Institute of Botany Academy of Sciences of the Czech Republic Třeboň Czech Republic.
Ecol Evol. 2017 Nov 30;8(1):435-440. doi: 10.1002/ece3.3541. eCollection 2018 Jan.
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 ( ) as the combined, limiting effect of biotic interactions and environmental filtering on trait expression (i.e., the mean value and range of functional traits). 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, for example, 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. 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). The relative ease of calculation and dimensionless nature of 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 (1) among communities from different regions, (2) on different traits across similar environmental gradients, and (3) for the same trait across different gradient types.
与生物和非生物力量相关的复杂过程会对植物群落的组装和组成施加限制。量化这些限制因素对不同环境梯度下以及不同群落中植物功能性状的影响仍然具有挑战性。我们将生态限制（ ）定义为生物相互作用和环境过滤对性状表达（即功能性状的平均值和范围）的综合限制作用。在此，我们提出了一组新的参数，通过扩展性状梯度分析（TGA）方法来量化这种限制。关键参数是生态限制，它是无量纲的，可以在各种尺度上进行测量，例如在种群和群落水平上。它有助于比较生态限制对不同环境梯度下以及群落内部和群落之间性状表达的影响。我们以澳大利亚西南部花岗岩露头沿干旱梯度的14种木本植物的树皮厚度为例，说明了所提出参数的应用。我们发现环境压力增加与树皮厚度表达的生态限制强度之间存在正相关。此外，来自压力更大栖息地（浅层土壤且阳光直射位置的灌丛）的植物比来自更适宜栖息地（深层土壤且遮蔽位置的林地）的植物在树皮厚度上表现出更高的生态限制。 的计算相对简便且无量纲的性质使其能够在各种尺度上轻松应用，并具有广泛的适用性。因此，它有可能推进对塑造性状表达的生态过程的机制理解。新参数未来的一些应用可能包括研究生态限制的模式：（1）不同地区群落之间的生态限制模式；（2）相似环境梯度下不同性状的生态限制模式；（3）不同梯度类型下同一性状的生态限制模式。
