Abstract:

As the most sensitive biological groups to the surrounding environment in the lake ecosystem, the community structure and diversity of microorganisms are important basis for matter cycle and ecological balance. In this study, microbial morphology and molecular identification were used to explore the temporal and spatial evolution characteristics of the dominant species of culturable filamentous fungi in spring, summer, and autumn of the Nam Co Lake, located in the Qinghai-Tibet Plateau. Eight environmental factors were measured, and the effects of the factors on the change of filamentous fungal population structure were analyzed comprehensively by using difference analysis, correlation analysis, and temporal and spatial heterogeneity analysis. The results showed that 921 strains of filamentous fungi were isolated and purified in the Nam Co Lake in spring, and were classified into 20 genera and 62 species; 1 412 strains were classified into 22 genera and 47 species in summer; and 1 026 strains were classified into 13 genera and 47 species in autumn. The dominant species include Penicillium commune, Penicillium vinaceum, Mucor hiemalis, Penicillium crustosum and Penicillium griseoroseum, and 23 other species. The niche data showed that the spatial, temporal, and spatiotemporal niche widths of dominant species ranged from 0.017 to 0.942, 0.333 to 0.979, and 0.006 to 0.314, respectively, and high overlap is the main type of niche overlap. The replacement rate of dominant species between summer and autumn was the highest (95%), followed by that between spring and summer (84%), and that between spring and autumn was the lowest (77%). There were significant differences in some environmental factors between different seasons (P<0.05), and environmental factors in different seasons had different effects on different dominant species. The community structure of dominant species was more affected by season than by space. The above results indicate that Nam Co Lake is rich in culturable filamentous fungi resources, with high seasonal replacement rate of dominant species and intense interspecific competition, and the community structure is unstable. Filamentous fungi have different dominance in different environments, so changes in environmental factors are important in shaping the diversity and composition of filamentous fungi in different seasons. Compared with other species (protozoa), the dominant taxa of filamentous fungi are more sensitive to environmental changes. Using this property, the dynamic composition characteristics of the dominant species can be used as microbial indicators of the changes of physicochemical factors in water, with a view to future applications in water quality monitoring and climate change.

Key words: Plateau lake, culturable filamentous fungi, dominant species, ecological niche, space-time evolution, environmental factors

摘要：

微生物作为湖泊生态系统中最易受周边环境影响的生物类群，其群落结构和多样性是决定物质循环、保持生态平衡的重要基础。以青藏高原纳木措湖为研究对象，用微生物形态学和分子生物学鉴定法，探究纳木措春、夏、秋3个季节的水体可培养丝状真菌优势种的时空演变特征；测定了8种水环境因子，采用差异性分析、相关性分析、时空异质性分析等方法，综合分析水环境因子对丝状真菌种群结构变化的影响。结果表明，纳木措春季共分离、纯化出水体丝状真菌921株，归为20属62种；夏季1412株，归为22属47种；秋季1026株，归为13属47种；优势种包括普通青霉Penicillium commune、酒色青霉Penicillium vinaceum、冻土毛霉Mucor hiemalis、壳青霉Penicillium crustosum以及灰玫瑰青霉Penicillium griseoroseum等23种。生态位数据显示，优势种的空间、时间以及时空生态位宽度值的区间分别为0.017—0.942、0.333—0.979、0.006—0.314，生态位重叠值以高度重叠为主。经计算，夏季与秋季的优势种更替率最高（95%），春季与夏季次之（84%），春季与秋季最低（77%），且不同季节间的部分环境因子存在显著差异（P<0.05），各季节的水环境因子对不同优势种的影响各异，优势种的群落结构受时间资源的影响大于空间资源。以上结果说明，纳木措水体可培养丝状真菌资源丰富，优势种季节更替率较高，种间竞争激烈，群落结构不稳定，丝状真菌在不同的环境中有着不同的优势度，因此环境因子的变化是塑造各季节丝状真菌多样性和组成差异的重要原因。相较于其他物种（原生动物），丝状真菌的优势类群对环境变化有着更敏感的响应；利用这种特性，可将其优势物种的动态组成特征作为水体理化因子变化的微生物指标，以期在未来应用于水质监测和气候变化中发挥作用。

关键词: 高原湖泊, 可培养丝状真菌, 优势种, 生态位, 时空演变, 环境因子