Pattern Of Aquatic Biodiversity And Driving Forces Of Alpine Micro-Waterbodies In Gaoligong Mountain,China

The alpine microwater-body(MWB)ecosystem in Gaoligong Mountain northwest Yunnan Province,China is of great significance to the formation and maintenance of regional biodiversity.Alpine MWB has its unique ecological properties,which are mainly reflected in the large number and high habitat heterogeneity,these properties providing a very rich habitat diversity for aquatic organisms.Therefore,alpine MWB has an important and obvious contribution to species richness in large-scale areas in terms of species richness.Alpine MWB represents a specific type of freshwater ecosystem,due to the lack of research attention,its biodiversity distribution patterns and driving forces have not been deeply understood.In this research,in order to explain the formation,maintainace and driving forces of aquatic biodiversity in alpine MWB in Gaoligong Mountain,northwest Yunnan Province,firstly,water samples have been collected 3 times in two seasons and 3 catchments in the area where located at the alpine vallay of Gaoligong Mountain.After the test of water quality in field and in lab,the effects of seasonality and catchment separation on MWB environmental factors were analyzed.Based on the obtained environmental data,the taxa identification of 7,347 MWB specimens(mainly are benthic animals)collected during the same time with the water samples were carried out,followed by the ecological statistical analysis.Attempted to explain the relationship between the biodiversity and the environmental factors of this specific ecosystem by analyzing the different dimensions of aquatic biodiversity in alpine MWB.Secondly,the formation and maintenance mechanisms of alpine MWB community was analyzed from the perspective of the classic theory of island biogeography which was meta-community.Finally,the effects of hydrological connection on biodiversity of MWB has been revealed.The results summarized as follow:(1)Through the measurement and corresponding analysis of the extinction variable and isolation variable of micro-water environment,revealed that the aquatic environment of the MWB cascaded system has a high degree of environmental heterogeneity,which could even be observed at an extreme fine scale with a spacedistance less than 1 m.In addition,the differences and trends of environmental heterogeneity in different seasons and catchments also proveed that compared with spatial distance,catchment unit was an ideal regional division unit for exteme fine scale aquatic ecology research.(2)From the perspective of species diversity(SD),functional diversity(FD)and taxonomic resolusion(TR)respectively,the aquatic bio-diversity of MWB were analysed by the spatial and temporal scale of seasons and catchments.The results showed that ? diversity was significantly affected by seasonal dynamic(p < 0.001),while,? diversity was affected by catchment spatial variation(the coefficient of variation of diversity was the highest at 0.32).However,the FD did not show significant catchment(p > 0.05)and seasonal(p = 0.655)differences.In addition,there was a correlation between different TR,which the genus level could best restore the bio-diversity information of species level(r = 0.694,p < 0.001).When faced to specific research issues,it is reasonable to consider the appropriate classification and identification practice with high efficiency and good explanatory value for the real diversity information.(3)From the perspective of environmental factors and community structure,the characteristics and dynamic processes of community structure between different seasons and different catchments were analyzed.The results showed that in terms of species richness and abundance,the community structure in the same catchment changed greatly in different seasons.In the rainy season,the species richness was 30,including 22 in AU and 23 in AD regions.The dominant taxa were Chironomus,Psectrocladius and Limnodrilus.The species richness in the dry season was 20,including 14 in AU,11 in AD and 16 D.The dominant taxa were Chironomus,Hydaticus and Limnodrilus.Combined with the analysis of the community and environmental factors,it is found that the formation of the community in this region is not mainly driven by environmental factors,but by species dispersal.In addition,the community structure in this region exhibited turnover in rainy season and nestedness in dry season,which may be related to the loss and recovery rate of species caused by seasonal freezing,a strong disturbance to the species in the community.(4)The cascaded and isolated MWB were selected to measure the water environmental factors,and the aquatic organisms were classified and identified.Theresults showed that the more MWBs connected,the species richness was stable above70% of the study region's potential richness(more than 20% above random average).It suggested that the connectivity had significant effects on the maintenance of species richness.But the environmental factors have no direct effects on species richness.Interestingly,in the area AU,5 of the 7 MWBs containing all the species were located at both ends of the cascaded system.While,in area AD,7 of the 8 MWBs containing all species were located at both ends of the cascaded system.It suggested that the MWBs located at the foremost end of the cascaded system showed an ‘edge effect',where the peripheral zones usually attract more endemic species than the central ones,with higher species richness and population size.These above results indicated that the formation and maintenance of aquatic biodiversity patterns in alpine MWBs were mainly driven by the dispersal capacity of aquatic organisms,hydrological state and water connectivity,while other environmental factors,especially extinction variables,were not the key environmental factors affecting the biodiversity in alpine MWBs.This study proposes an explanation of the community structure spatial processes and a new prospective for biodiversity conservation,making the MWB as a research and conservation critical site.Since alpine MWB ecosystem has significant effects on the maintenance of watershed biodiversity,further research on such small and crucial ecosystem is encouraged.