水位变化驱导的泛滥平原典型生境鱼类beta多样性动态

Beta Diversity Dynamics of Fish Communities Inhabiting Typical Floodplain Habitats Driven by Water Level Variation

泛滥平原生态系统由流水和静水两类典型生境组成,鱼类群落在不同水文周期和水位波动驱导下经历剧烈的beta多样性变动。为解析此生态系统过程,分别度量了周期性水位变化下泛滥平原流水和静水生境鱼类的总beta多样性(TBI)、beta增加(D_(gain))和beta丧失(D_(loss))的时间变化,可为流域鱼类资源保护提供理论支撑;通过进一步计算各物种对beta多样性格局的贡献(SCBD),甄别出流水和静水生境中响应水位变化的关键鱼类物种。结果表明,随水位下降,菜子湖静水和流水生境鱼类群落总beta多样性的时间变化主要受物种丧失过程的影响,且流水生境的D_(loss)显著高于D_(gain)(P<0.05),反映了随洪泛退散流水生境中鱼类群落资源的急剧减退。随着水位下降,驱导beta多样性变动的关键物种如黄颡鱼(Tachysurus fulvidraco)、长须拟鲿(Tachysurus longibarbus)、光唇蛇鮈(Saurogobio gymnocheilus)等河流型鱼类的SCBD在流水和静水生境均表现出降低的趋势;而翘嘴鲌(Culter alburnus)、团头鲂(Megalobrama amblycephala)、花鲐骨(Hemibarbus maculatus)、鲐箴(Hyporhamphus intermedius)和鲫(Carassius auratus)等湖泊广布型物种的SCBD随水位的降低均明显升高。静水和流水生境中的物种SCBD指数变化(ΔSCBD)与多度变化呈极显著正相关(P<0.001),表明水位变化导致的群落结构差异以及各物种资源量变动均为造成鱼类群落beta多样性格局变迁的影响因素。

The floodplain ecosystem consists of two typical habitats,lentic and lotic.Previous research has shown that the beta diversity of fish community structure in the lentic and lotic habitats of the floodplain undergo drastic changes,driven by changing hydrological regimes and flood pulses.Differences in beta diversity indicates differences in both species richness and abundance of the fish community.In this study,Caizi Lake basin was selected as a case study to explore the dynamics of these ecosystems.The temporal changes of overall beta diversity(TBI),beta gain(D_(gain))and beta loss(D_(loss))of fish communities in the lentic and lotic floodplain habitats were analyzed in the wet and dry seasons.Further,key fish species that respond profoundly to flood pulses in lentic and lotic habitats were identified by calculating the Species Contribution to Beta Diversity(SCBD).We aimed to better understand the influence of periodical water level variation on fish community structure in the lentic and lotic habitats as well as the dynamics of key fish species that lead to differences in community structure.Caizi Lake is connected to the Yangtze River by Changhe River and Zongyang sluice was constructed at the Changhe River cove in Caizi Lake to regulate the lake water level.Based on the sluice water level record,fish sampling was carried out in August(high water level)and December(low water level)at ten sites in both the Changhe River(lotic habitat)and Caizi Lake(lentic habitat).The body length and body weight of all specimens were measured,and the species was identified.Results show that the periodic water level fluctuation resulted in dramatic migrations that alter species composition.With declining water levels,the overall beta diversity(TBI)of fish in both lentic and lotic habitats decreases.However,D_(loss) in the lotic habitat was significantly higher than D_(gain)(P<0.05),indicating a dramatic decline of lotic fish resources.During the period of receding water level,the SCBD values of riverine fish species,such as yellow catfish,(Tachysurus fulvidraco),long-bearded catfish(Tachysurus longibarbus),and gudgeons(Saurogobio gymnocheilus)in both lentic and lotic habitats decreased.However,the SCBD values of some lake residents such as grass carps(Culter alburnus),Wuchang breams(Megalobrama amblycephala),spotted steeds(Hemibarbus maculatus),Asian pencil halfbeaks(Hyporhamphus intermedius)and crucian carps(Carassius auratus)increased in both habitats.There was a significant positive correlation between changes in species abundance and SCBD(ΔSCBD)in both lentic and lotic habitats(P<0.001),indicating that the changes in both fish community structure and abundance that are triggered by flood pulses can influence variations in beta diversity.In general,variation of the hydrological regime affects the beta diversity of fish in lotic habitats more than in lentic habitats,so conservation of lotic habitats should receive preferential treatment.