金沙江丰富类和稀有类浮游真核微生物的分布特征与影响因素

浮游真核微生物通常由少数丰富类和大量稀有类组成，二者在维持水生生态系统健康稳定方面具有重要作用.目前对大型筑坝河流中这两类真核微生物的生物地理分布模式所知甚少.以我国西南梯级水电开发河流金沙江为研究区域，对比分析丰富类和稀有类浮游真核微生物在不同河段的分布特征，解析影响两类微生物空间分布的主导因素.结果表明，相比上游自然河段，金沙江浮游真核微生物的α多样性在梯级大坝河段显著升高，稀有类的α多样性增长比高于丰富类.浮游真核丰富类和稀有类微生物的群落组成在不同河段间存在显著差异，其中Vermamoeba属等优势属的相对丰度在两河段间同样存在明显差异.影响丰富类和稀有类浮游真核微生物群落组成的关键地化因子有海拔和pH等，两类微生物群落相似性与地理距离和环境异质性均符合距离衰减关系，其群落构建均受扩散限制和环境筛选共同影响；方差分解分析和偏Mantel检验结果显示扩散限制是影响丰富类和稀有类分布的主要驱动因素.研究结果为我国西南缺资料区水电开发河流中微生物的地理分布模式和生态响应提供数据支持.

Distribution Characteristics and Influencing Factors of Abundant and Rare Planktonic Microeukaryotes in Jinsha River

Planktonic microeukaryotes are usually composed of a few abundant species and a large number of rare species, which play an important role in maintaining the health and stability of aquatic ecosystems. At present, little is known about the biogeographical distribution patterns of these two groups of microeukaryotes in large damming rivers. This study analyzed the distribution patterns of abundant and rare planktonic microeukaryotes and the dominant factors affecting their spatial distributions in the Jinsha River, one of the largest rivers in southwestern China that is strongly regulated by cascade dams. The results showed that the alpha diversity of planktonic microeukaryotes in the Jinsha River was higher in the cascade dam reach than that in the upstream natural reach, and the increase in alpha diversity of rare species was larger than that of rich species. There were significant differences in microbial community composition among different river sections, and the relative abundances of the dominant genera such as Vermamoeba shared by them were also significantly different between the two river sections. The results of distance decay analysis revealed that the geographic distribution patterns of rare and abundant taxa were jointly influenced by environmental heterogeneity and dispersal limitation, and the results of variance decomposition analysis and partial Mantel further indicated that dispersal limitation was the dominant ecological process. The results provided data support for the distribution and ecological response of microorganisms in rivers in the areas lacking data in Southwest China.