School of Biological Sciences, The University of Queensland, St Lucia, Qld, 4072, Australia.
College of Law, Australian National University, Canberra, ACT, 2600, Australia.
New Phytol. 2022 Nov;236(3):839-851. doi: 10.1111/nph.18418. Epub 2022 Aug 20.
A range of functional trait-based approaches have been developed to investigate community assembly processes, but most ignore how traits covary within communities. We combined existing approaches - community-weighted means (CWMs) and functional dispersion (FDis) - with a metric of trait covariance to examine assembly processes in five angiosperm assemblages along a moisture gradient in Australia's subtropics. In addition to testing hypotheses about habitat filtering along the gradient, we hypothesized that trait covariance would be strongest at both ends of the moisture gradient and weakest in the middle, reflecting trade-offs associated with light capture in productive sites and moisture stress in dry sites. CWMs revealed evidence of climatic filtering, but FDis patterns were less clear. As hypothesized, trait covariance was weakest in the middle of the gradient but unexpectedly peaked at the second driest site due to the emergence of a clear drought tolerance-drought avoidance spectrum. At the driest site, the same spectrum was truncated at the 'avoider' end, revealing important information about habitat filtering in this system. Our focus on trait covariance revealed the nature and strength of trade-offs imposed by light and moisture availability, complementing insights gained about community assembly from existing trait-based approaches.
一系列基于功能特征的方法已被开发出来，以研究群落组装过程，但大多数方法忽略了特征在群落内部的变化。我们结合了现有的方法——群落加权均值（CWMs）和功能离散度（FDis）——以及特征协方差的度量，来研究澳大利亚亚热带地区沿湿度梯度的五个被子植物群落在五个被子植物群落在沿湿度梯度的组合过程。除了检验关于梯度上栖息地过滤的假设外，我们还假设特征协方差在湿度梯度的两端最强，在中间最弱，反映了与光捕获相关的权衡在生产力高的地方和在干燥的地方的水分胁迫。CWMs 揭示了气候过滤的证据，但 FDis 模式不太明显。正如假设的那样，特征协方差在梯度的中间最弱，但在第二干燥的地点出人意料地达到峰值，这是由于出现了明显的耐旱-耐旱回避谱。在最干燥的地点，同样的谱在“回避者”一端被截断，揭示了该系统中栖息地过滤的重要信息。我们对特征协方差的关注揭示了光和水分可用性所带来的权衡的性质和强度，这补充了从现有的基于特征的方法中获得的关于群落组装的见解。
