Department of Tisza Research, Danube Research Institute, Centre for Ecological Research, 18/c. Bem square, 4026, Debrecen, Hungary.
Department of Hydrobiology, University of Debrecen, P.O. Box 57, 4010, Debrecen, Hungary.
Sci Rep. 2020 Nov 11;10(1):19599. doi: 10.1038/s41598-020-76645-7.
Environmental filtering and limiting similarity are those locally acting processes that influence community structure. These mechanisms acting on the traits of species result in trait convergence or divergence within the communities. The role of these processes might change along environmental gradients, and it has been conceptualised in the stress-dominance hypothesis, which predicts that the relative importance of environmental filtering increases and competition decreases with increasing environmental stress. Analysing trait convergence and divergence in lake phytoplankton assemblages, we studied how the concepts of 'limiting similarity' versus 'environmental filtering' can be applied to these microscopic aquatic communities, and how they support or contradict the stress-dominance hypothesis. Using a null model approach, we investigated the divergence and convergence of phytoplankton traits along environmental gradients represented by canonical axes of an RDA. We used Rao's quadratic entropy as a measure of functional diversity and calculated effect size (ES) values for each sample. Negative ES values refer to trait convergence, i.e., to the higher probability of the environmental filtering in community assembly, while positive values indicate trait divergence, stressing the importance of limiting similarity (niche partitioning), that is, the competition between the phytoplankters. Our results revealed that limiting similarity and environmental filtering may operate simultaneously in phytoplankton communities, but these assembly mechanisms influenced the distribution of phytoplankton traits differently, and the effects show considerable changes along with the studied scales. Studying the changes of ES values along with the various scales, our results partly supported the stress-dominance hypothesis, which predicts that the relative importance of environmental filtering increases and competition decreases with increasing environmental stress.
环境过滤和限制相似性是那些影响群落结构的局部作用过程。这些作用于物种特征的机制导致群落内部的特征趋同或趋异。这些过程的作用可能会随环境梯度而变化，这在应激主导假说中得到了概念化，该假说预测，随着环境应激的增加，环境过滤的相对重要性增加，而竞争减少。通过分析湖泊浮游植物组合中的特征趋同和趋异，我们研究了“限制相似性”与“环境过滤”的概念如何应用于这些微观水生群落，以及它们如何支持或反驳应激主导假说。我们使用一种 null 模型方法，通过 RDA 的典型轴来研究浮游植物特征沿环境梯度的发散和收敛。我们使用 Rao 的二次熵作为功能多样性的度量，并为每个样本计算了效应大小（ES）值。负的 ES 值表示特征趋同，即环境过滤在群落组装中的概率更高，而正的 ES 值则表示特征趋异，强调了限制相似性（生态位分割）的重要性，即浮游植物之间的竞争。我们的结果表明，限制相似性和环境过滤可能同时在浮游植物群落中起作用，但这些组装机制对浮游植物特征的分布有不同的影响，而且这些影响随着研究的尺度而发生相当大的变化。通过研究 ES 值随各种尺度的变化，我们的结果部分支持了应激主导假说，该假说预测，随着环境应激的增加，环境过滤的相对重要性增加，而竞争减少。
