MTA Centre for Ecological Research, Danube Research Institute, Karolina út 29, H-1113, Budapest, Hungary.
National University of Public Service, Faculty of Water Sciences, 6500, Baja, Bajcsy-Zsilinszky utca 12-14, Hungary.
Sci Rep. 2019 Oct 31;9(1):15749. doi: 10.1038/s41598-019-52304-4.
The stress dominance hypothesis (SDH) postulates that strong environmental gradients drive trait convergence in communities over limiting similarity. Previous studies, conducted mostly with terrestrial plant communities, found controversial evidence for this prediction. We provide here the first test for SDH for epiphytic diatoms. We studied community assembly in diatom communities of astatic ponds. These water bodies serve as a good model system for testing SDH because they exhibit stress gradients of various environmental factors. Functional diversity of diatom communities was assessed based on four traits: (1) combined trait reflecting the trade-off between stress tolerance and competitive dominance, (2) cell size, (3) oxygen requirement and (4) N-uptake strategy. According to our results, salinity, pH and the width of the macrophyte belt appeared as significant predictors of the trait convergence/divergence patterns presumably acting through influencing the availability of carbon dioxide and turbidity. Lower trait diversity was found in turbid, more saline and more alkaline ponds and functional diversity was higher in transparent, less saline and less alkaline ponds. Overall, our results supported the stress dominance hypothesis. In habitats representing increased environmental stress, environmental filtering was the most important community assembly rule, while limiting similarity became dominant under more favourable conditions.
胁迫主导假说（SDH）认为，在限制相似性的情况下，强烈的环境梯度会导致群落中特征的趋同。先前的研究主要针对陆生植物群落进行，对这一预测存在争议性的证据。我们在此为附生硅藻群落提供了对 SDH 的首次检验。我们研究了静态池塘中硅藻群落的群落组装。这些水体是检验 SDH 的良好模型系统，因为它们表现出各种环境因素的胁迫梯度。硅藻群落的功能多样性基于四个特征进行评估：（1）反映耐胁迫性和竞争优势之间权衡的综合特征，（2）细胞大小，（3）氧气需求和（4）氮吸收策略。根据我们的结果，盐度、pH 值和大型植物带的宽度似乎是特征趋同/发散模式的重要预测因子，可能通过影响二氧化碳和浊度的可利用性起作用。在浑浊、盐分更高和碱性更强的池塘中，特征多样性较低，而在透明、盐分较低和碱性较弱的池塘中，功能多样性较高。总体而言，我们的结果支持胁迫主导假说。在代表环境胁迫增加的生境中，环境过滤是最重要的群落组装规则，而在更有利的条件下，限制相似性变得占主导地位。
