江湖阻隔对长江中下游湖泊鱼类群落分类多样性的影响

基于1950s以来的长江中下游湖泊鱼类调查数据,分析通江湖泊与阻隔湖泊的鱼类分类多样性差异,以及通江和阻隔湖泊鱼类分类多样性的时间序列变化,探讨江湖阻隔对鱼类多样性的影响。结果显示,阻隔湖泊鱼类物种数、平均分类差异指数(Δ⁺)和分类差异变异指数(Λ⁺)平均值分别为48.47±14.64、74.02±3.09和736.89±33.80;通江湖泊为76.22±14.40、78.31±0.98和697.31±25.53。阻隔湖泊物种数和Δ⁺值显著低于通江湖泊(P<0.001),而阻隔湖泊Λ⁺值显著高于通江湖泊(P=0.002),表明阻隔湖泊物种间亲缘关系更近,均匀度下降,即物种分类单元减少,且集中分布于某几个分类阶元,稳定性变差。典型通江与阻隔湖泊鱼类群落分类多样性的时间变化分析发现,两种类型湖泊的鱼类物种数和Δ⁺值均随时间推移整体呈现下降趋势,Λ⁺值整体呈现升高趋势;并且阻隔湖泊的Λ+值随阻隔时间增加而大幅上升,Δ⁺和Λ^+...

RIVER-LAKE DISCONNECTION ON FISH TAXONOMIC DISTINCTNESS IN LAKES FROM MIDDLE AND LOWER REACHES OF THE YANGTZE RIVER

In the middle-lower reach of the Yangtze River, there are many lakes with intensive fish biodiversity, which are connected with the Yangtze mainstream historically. Since the 1950s, most of these lakes have experienced river-lake disconnection by anthropogenic impacts, leading to remarkable biodiversity decline of fish in these lakes. Based on the published literatures about fish assemblages in lakes, the taxonomic distinctness and temporal changes of fish communities in the connected lakes and disconnected lakes were examined by using two taxonomic diversity indices (average taxonomic distinctness, Δ+ and variation in taxonomic distinctness, Λ+), to assess the impact of river-lake disconnection. The results indicated that disconnected lakes showed significantly lower species richness and Δ+ values (average values of 48.47±14.64 and 74.02±3.093, respectively) than connected lakes (average values of 76.22±14.40 and 78.31±0.98, respectively; P<0.001), indicating the loss of fish diversity. On the contrary, the disconnected lakes showed significantly higher Λ+ values (average values 736.89±33.80) than connected lakes (average values of 697.31±25.53; P=0.002), indicating the increasing unevenness of taxonomic distinctness. Our analysis of temporal changes showed that species richness and Δ+ generally declined, and Λ+ generally increased through time within representative connected and disconnected lakes. However, the species richness, Δ+ and Λ+ values of the connected lake fluctuated over time, and the Λ+ increased significantly over time. These mean that connected lakes were also affected by various disturbances, which led to the decline of taxonomic diversity and the distribution of fish in disconnected lakes was more concentrated in some taxa resulting high unevenness and low stability in the community. Based on our results, we suggested to restore the fish diversity in the middle and lower reaches of the Yangtze River by recovering the connection between the lakes and the Yangtze mainstream, improving the quality of fish habitat through water environment management, and scientifically adjusting the fish community structure.