Zhang Min, García Molinos Jorge, Zhang Xiaolin, Xu Jun
College of Fisheries, Huazhong Agricultural University, Hubei Provincial Engineering Laboratory for Pond Aquaculture, Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Wuhan, China.
Arctic Research Center, Hokkaido University, Sapporo, Japan.
Front Plant Sci. 2018 Mar 27;9:387. doi: 10.3389/fpls.2018.00387. eCollection 2018.
Human activities and the consequent extirpations of species have been changing the composition of species assemblages worldwide. These anthropogenic impacts alter not only the richness of assemblages but also the biological dissimilarity among them. One of the main gaps in the assessment of biodiversity change in freshwater ecosystems is our limited understanding regarding how taxonomic and functional facets of macrophyte assemblages respond to human impacts on regional scales. Here, we assess the temporal (before 1970s against after 2000s) changes in taxonomic and functional richness and compositional dissimilarities, partitioned into its turnover and nestedness components, of freshwater macrophyte assemblages across the floodplain lakes of the Yangtze River in China. We found that functional and taxonomic assemblage differentiation occurred simultaneously under increasing human impact, concomitant to a general decrease in functional and taxonomic richness. However, this effect weakened when the historical level of taxonomic dissimilarity among assemblages was high. Macrophyte species with large dispersal range and submersed life form were significantly more susceptible to extirpation. The impact of human activities on differentiation was complex but habitat loss and fishery intensity were consistently the main drivers of assemblage change in these lakes, whereas water quality (i.e., light pollution and nutrient enrichment) had weaker effects. Further, macrophyte taxonomic and functional differentiation was mainly driven by the nestedness component of dissimilarity, accounting for changes in assemblage composition related to changes in species richness independent of species replacement. This result, markedly different from previous studies on freshwater fish assemblages conducted in these lakes, represents a novel contribution toward achieving a more holistic understanding of how human impacts contribute to shape community assemblages in natural ecosystems.
人类活动以及随之而来的物种灭绝一直在改变着全球物种组合的构成。这些人为影响不仅改变了组合的丰富度，还改变了它们之间的生物差异。在评估淡水生态系统生物多样性变化方面，主要差距之一是我们对大型植物组合的分类学和功能层面如何在区域尺度上响应人类影响的理解有限。在此，我们评估了中国长江漫滩湖泊中淡水大型植物组合在分类学和功能丰富度以及组成差异方面的时间变化（20世纪70年代之前与21世纪之后进行对比），并将其组成差异划分为周转和嵌套成分。我们发现，在人类影响增加的情况下，功能和分类组合分化同时发生，与此同时功能和分类丰富度普遍下降。然而，当组合之间分类差异的历史水平较高时，这种影响会减弱。具有较大扩散范围和沉水生活型的大型植物物种更容易灭绝。人类活动对分化的影响很复杂，但栖息地丧失和渔业强度一直是这些湖泊中组合变化的主要驱动因素，而水质（即光污染和营养物富集）的影响较弱。此外，大型植物的分类和功能分化主要由差异的嵌套成分驱动，这解释了与物种丰富度变化相关的组合组成变化，而与物种替代无关。这一结果与之前在这些湖泊中对淡水鱼类组合的研究明显不同，为更全面地理解人类影响如何塑造自然生态系统中的群落组合做出了新贡献。
