| The unique and complex river-lake ecosystem of the Yangtze River has nursed an extremely rich biodiversity.In recent years,a series of human disturbance activities,such as sluice building and embankment building,have blocked and divided the lakes originally connected with the Yangtze River,resulting in artificial barrier between the river and the lake,which has become a key factor threatening the fish community structure.However,in the past,the effects of river lake barrier on fish diversity were mainly studied at the level of species diversity,and there were few studies on the taxonomic structure and population genetic diversity of fish.In this paper,we selected the representative barrier lakes and lakes in the Yangtze River basin as the study area,and analyzed the effects of river and lake barriers on the diversity composition and taxon structure changes of fish by collating the historical survey data of wild fish resources.The effects of river-lake barrier on the genetic diversity of fish populations were investigated with different ecological types of fish as research objects.The results are as follows:The changes of fish taxonomic structure and functional diversity of West Dongting Lake,Poyang Lake,Huangguai Lake,Xiliang Lake,Zhangdu Lake and Chi Lake were analyzed.It was found that the number of fish species in all six lakes decreased to different degrees,and the number of fish species lost was the least in West Dongting Lake and Poyang Lake.The G index and F index of all the lakes decreased to different degrees,and the G index and F index of West Dongting Lake,Poyang Lake and Huanggai Lake were generally higher than those of the other unconnected lakes.In general,the functional diversity index of fish showed a decreasing trend,among which SES.MFD first decreased and then tended to be stable.There was a positive correlation between the number of species and genera of fishes in each lake,which could be well fitted by the linear equation,and the number of species and genera was consistent(P=0.191).The frequency distribution of the genera containing the same number of species decreases with the increase of the number of species contained in each genus,and the R~2 value after fitting with the power model approaches 1.Mitochondrial molecular markers showed that haplotype diversity of Culter alburnus,Carassius auratus and Monopterus albus carp populations were characterized by high haplotype diversity and high nucleotide diversity.Channa argus population showed high haplotype diversity and low nucleotide diversity.The haplotype phylogenetic trees of all populations,such as C.alburnus,C.argus and C.auratus were mosaic,but haplotypes of M.albus were mosaic,and haplotypes Hap16-18,Hap7 and Hap9 were independent branches,respectively.The genetic distance between the migratory species C.alburnus and the populations of the unconnected lakes was relatively large,but there was no significant difference between the populations of the sedentary species.Microsatellite genetic diversity analysis of the populations showed that there were two genetic lineage among the six geographic populations,and the populations of(half)linking lakes and unconnected lakes populations showed significant genetic differentiation.Cluster analysis showed that the populations of(half)linking lakes and unconnected lakes populations were clustered into one cluster,while the populations of unconnected lakes populations were clustered into one cluster.In general,significant changes were found in the fish species diversity and functional diversity under the background of river-lake disconnection,especially in the lake barrier.However,after the ecological environment became stable,the species taxonomic structure still maintained its original characteristics.At the same time,river-lake disconnection had different effects on the population genetic diversity of different ecological types of fish,which provided supplementary information at different levels for assessing the changes of fish diversity under river-lake disconnection. |
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