拉萨河中下游原生动物群落物种分布格局及其驱动因素

了解拉萨河中下游原生动物群落物种分布格局及其驱动因素，为拉萨河中下游生物多样性保护及可持续利用提供基础资料。选取了拉萨河中下游17个样点，于2015年5月、8月和2016年11月进行原生动物定性和定量样品采集，共采集水样153份，分析物种组成、生物多样性及其与环境因子之间的关系，确定该流域原生动物类群组成中稀有种、偶见种和常见种对物种多样性的贡献、生物多样性格局及群落与理化因子相关性，结果表明：（1）3个季节，稀有种80种，占总物种的40%；偶见种95种，占总物种的48%；常见种21种，占总物种的11%；恒见种1种，占总物种的0.5%。（2）拉萨河中下游原生动物物种类群组成中偶见种是原生动物群落物种多样性格局的重要贡献者。（3）多样性指数表明，Richness指数和Margalef指数春季和夏季高于秋季，Shannon-Wiener指数和Simpson指数春季高于秋季高于夏季。（4）基于Bray-Curtis距离的主坐标分析和相似性分析结果表明，拉萨河中下游原生动物群落结构在不同季节和不同流域均具有显著差异，且流域差异相比季节差异较大。（5）根据Mantel检验分析原生动物与环境因子的相关性，结果表明，在所测定环境因子中，水温（WT）、总溶解性固体（TDS）、盐度（Salt）、电导率（EC）、总磷（TP）及溶解氧（DO）是影响原生动物群落结构的主要环境因子。

Species Distribution and Factors Driving the Protozoan Community in the Middle and Lower Lhasa River

Lhasa River is one of the five largest tributaries of the Yarlung Zangbo River and plays important roles as an ecological corridor, in regional climate regulation, as a water source and in maintaining biodiversity in Tibet. The current study explored species distribution patterns and factors influencing the protozoan community in the middle and lower reaches of Lhasa River, aiming to provide basic data for conserving biodiversity and water resources. In May (spring), August (summer) of 2015 and November (autumn) of 2016, qualitative and quantitative protozoan samples were collected at 17 sampling sites in the middle and lower reaches of the Lhasa River. Species composition and distribution patterns of the protozoan community and their correlation with physicochemical factors of the river water were then analyzed. Results show that: (1) A total of 197 protozoan species were identified during the three seasons, including 80 rare species, 95 occasional species, 21 common species, and 1 constant species, which accounted for 40%, 48%, 11% and 0.5% of the total species, respectively. (2) Occasional species were important contributors to the species diversity of the protozoan community in Lhasa River. (3) The Richness and Margalef indices were higher in spring and summer than in autumn, while the Shannon-Wiener and Simpson indices were higher in spring and autumn than in summer. (4) The results of principal coordinate analysis and similarity analysis based on Bray-Curtis distance showed that the protozoan community structure in the middle and lower reaches of Lhasa River varied significantly with season and river segment, with larger variations between river segments than between seasons. (5) The Mantel test was used to analyze the correlations between protozoan community parameters and environmental factors. Water temperature (WT), total dissolved solids (TDS), salinity (Salt), electrical conductivity (EC), total phosphorus (TP) and dissolved oxygen (DO) were the primary environmental factors affecting protozoan community structure.