BackgroundDidymosphenia geminata (Lingbye) M. Schmidt is a freshwater invasive benthic diatom native to oligotrophic systems of the Northern Hemisphere. Since 2010, freshwater systems of south-austral Chile, have experienced a progressive invasion of this species between 37° 18′ S and 54° 30′ S. This invaded area is characterized by biogeographic heterogeneity, anthropic pressure and lack of knowledge. The objective of this study was to analyze the effect of D. geminata on the community structure of benthic diatoms and the variability of this effect in Chilean rivers.MethodsThe data were collected between 2010 and 2017 and pre-treated using fourth-root transformation to construct a Bray-Curtis similarity matrix and a Principal Coordinate Analysis to identify groups of sites. The α diversity and β diversity were estimated and compared using univariate indexes and the Mann-Whitney test, respectively. We used Permutational multivariate analyses of variance (PERMANOVA) and PERMDISP to estimate the spatial variation of communities, and an Analysis of Percentage Similarity (SIMPER) was performed to identify the species which contributed to the similarity between the groups of sites.ResultsThe results suggest significant differences between invaded and noninvaded rivers (54% of the total variation); the univariate indexes showed greater richness (S), greater diversity (H′), and less species turnover in invaded rivers. The PERMANOVA indicated significant interaction between D. geminata and the basins; there was also a significant effect on the internal dispersion in the basins. The SIMPER analysis showed that the groups composed exclusively of invaded sites had high mean similarity in all basins and small pedunculated benthic diatoms showed a significant response to the presence of D. geminata.ConclusionWe found high variability in the community structures, that determine a strong segregation between non-invaded and invaded sites by D. geminata, and that the main effect of D. geminata on diatoms benthic was the homogenization of the communities. This is reflected in the increase in density of small stalked diatoms and the reduction of species turnover among rivers in the same basin, leading to the loss of community heterogeneity that overcomes the spatial heterogeneity in the area invaded in Chile.

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Didymosphenia geminata (Lingbye) M. Schmidt 对智利河流底栖硅藻群落影响的群落信号

背景Didymosphenia geminata (Lingbye) M. Schmidt 是一种淡水入侵底栖硅藻，原产于北半球的贫营养系统。自 2010 年以来，南南智利的淡水系统在南纬 37° 18' 和 54° 30' 之间经历了该物种的逐步入侵。该入侵区域的特点是生物地理异质性、人类压力和知识缺乏。本研究的目的是分析 D. geminata 对底栖硅藻群落结构的影响以及这种影响在智利河流中的变异性。 方法 数据收集于 2010 年至 2017 年之间，并使用四根变换进行预处理以构建Bray-Curtis 相似性矩阵和主坐标分析来识别站点组。α多样性和β多样性分别使用单变量指数和Mann-Whitney检验进行估计和比较。我们使用置换多元方差分析 (PERMANOVA) 和 PERMDISP 来估计群落的空间变异，并进行百分比相似性分析 (SIMPER) 来识别导致站点组之间相似性的物种。结果结果表明显着入侵和未入侵河流之间的差异（总变异的 54%）；单变量指数在入侵河流中表现出更大的丰富度（S），更大的多样性（H'）和更少的物种周转。PERMANOVA 表明 D. geminata 与盆地之间存在显着的相互作用；对盆地内部的弥散也有显着影响。SIMPER 分析表明，完全由入侵地点组成的群体在所有盆地中具有很高的平均相似性，小带蒂底栖硅藻对 D. geminata 的存在表现出显着的响应。结论我们发现群落结构的高度可变性，这决定了强烈的分离D. geminata 未入侵和入侵地点之间的差异，并且 D. geminata 对底栖硅藻的主要影响是群落的同质化。这体现在小茎硅藻密度的增加和同一流域河流之间物种周转的减少，导致群落异质性的丧失，克服了智利入侵地区的空间异质性。