The water-level regime is a major determinant of the community structure in river-floodplain systems. Chironomidae is a highly diverse insect family that plays a key role in the trophic structure and functioning of floodplain systems. However, we know little about how water-level oscillations affect the chironomid structure. Using a 9-year database, we investigated how the richness, density, and temporal β-diversity of chironomid larvae are affected by water-level oscillations and environmental variables in a tropical lake. We tested the hypotheses that (i) in high-water-level periods, the Chironomidae community is more similar (homogeneous) among sites within the lake; (ii) in low-water-level periods, the Chironomidae community is more variable, and that this is likely because (iii) the importance of environmental filtering is stronger in low-water-level periods than in high-water-level periods. We found a hump-shaped relationship between chironomid richness and density with water level, and a monotonic negative relationship between chironomid β-diversity and water level over the years. Chironomidae composition was structured by water-level oscillations during the high-water-level period, whereas during the low-water-level period, environmental filtering was the most important structuring factor. In addition, Chironomidae density and richness decreased in high- and low-water-level periods compared to intermediate-water-level periods, and temporal Chironomidae β-diversity increased in low-water-level periods and decreased in high-water-level periods. Our findings are important considering that extreme climatic events tend to increase in frequency and intensity in the future, which may increase the frequency of extreme low- and high-water-level periods in floodplain systems.

水位状况是河流泛滥平原系统群落结构的主要决定因素。摇蚊科是一个高度多样化的昆虫家族，在洪泛区系统的营养结构和功能中起着关键作用。然而，我们对水位振荡如何影响摇蚊结构知之甚少。我们使用一个 9 年的数据库，研究了热带湖泊中水位波动和环境变量如何影响摇蚊幼虫的丰富度、密度和时间 β 多样性。我们检验了以下假设：(i) 在高水位时期，摇蚊科群落在湖内地点之间更加相似（同质）；(ii) 在低水位时期，摇蚊科群落更加多变，这可能是因为（iii）环境过滤的重要性在低水位时期比在高水位时期更强。我们发现摇蚊丰富度和密度与水位之间呈驼峰状关系，多年来摇蚊β多样性与水位之间呈单调负相关。摇蚊科的成分在高水位期间由水位振荡构成，而在低水位期间，环境过滤是最重要的结构因素。此外，与中水位时期相比，摇蚊科在高、低水位时期的密度和丰富度有所下降，而摇蚊科β-多样性在低水位时期增加而在高水位时期减少.