Fish Diversity And Spatio-temporal Distribution Patterns In The Qilian Mountains

The Qilian Mountains are located on the northeastern edge of the Qinghai-Tibet Plateau（QTP）and serve as a vital water source and drainage area in the arid and semi-arid regions of northwestern China.The region also supports a rich diversity of endemic and endangered fish species.However,a comprehensive understanding of the detailed species inventory,diversity patterns,assemblage changes,and influencing factors of fish in the entire region remains unknown,hindering efforts to conserve biodiversity and assess ecological health.Here,we compiled a comprehensive database of fish species richness and distribution in the Qilian Mountains,based on a three-year field investigation and exhaustive data collection from literature,books,online databases and specimens deposited in the museum of Lanzhou University.Then,temporal and spatial distribution characteristics of the fish composition,αandβdiversity patterns and their influencing factors,and the impact of climate change on the distribution range of fish suitable habitats were discussed.The main findings of this study are as follows:1.A total of 78 fish species were found in the study area,belonging to 42 genera,17 families and 8 orders.Cypriniformes fishes dominate the regional fish fauna,followed by Gobiiformes and Siluriformes.There were 39 native species,belonging to 12 genera,6 families and 2 orders,and 38 exotic fish species,belonging to 30genera,16 families and 8 orders.We identified 45 species endemic to China in the Qilian Mountains,belonging to 20 genera,10 families and 3 orders.Four fish species were listed as national class II protected wildlife and 13 fish species were classified as aquatic wildlife with provincial class key protection,belonging to 8 genera,4 families and 2 orders,accounting for 33.3%of the native species.A total of 14 fish were categorized as threatened（i.e.,CR,EN and VU）,belonging to 10 genera,5 families and 2 orders,accounting for 35.9%of the native species.2.Cluster analysis results for 49 rivers or lakes,based on the Bray-Curtis coefficient,showed that the ichthyofauna composition was distinctively divided and corresponded to the six basins,which could be merged into the northern（Shiyang River Basin,Heihe River Basin and Shule River Basin）and southern（Yellow River Basin,Qinghai Lake Basin and Qaidam Basin）regions of the Qilian Mountains.This study also showed that adjacent rivers or basins shared higher biotic similarity,which is known as the distance decay of taxonomic similarity.The analysis of linear discriminant analysis（LDA）effect size（LEf Se）,similarity percentages（SIMPER）,and indicator species（ISA）indicated that the indicator species in the Yellow River Basin were distinct from those in the other basins,which may be caused by that these species were less affected by the uplift of the QTP than Schizothorax and Triplophysa.3.Through a comparison of distribution data for fish species in the Qilian Mountains from the past（the 1960s and 1980s）and present（the 2000s）,a temporal shift in species composition was observed,with an increase in invasive species and a decrease in native species.Furthermore,a decreasing Bray-Curtis dissimilarity coefficient among the six basins suggested an increasing similarity in fish composition over time,displaying a homogenization of species composition.The construction of hydraulic facilities and the presence of invasive species were found to be the main drivers of these changes.4.Based onαdiversity analysis,a higher taxonomic diversity of fish species was recorded in the middle reaches of the Qilian Mountains,while a lower taxonomic diversity was observed in both the upper and lower reaches.Multiple regression analysis showed that river length and slope were the most influential predictors of fishαdiversity in the Qilian Mountains.Analysis ofβdiversity showed that the fish composition in the Qilian Mountains exhibited a high degree of dissimilarity(β_sor=0.71,βcc=0.80).Species turnover and replacement components were the primary drivers ofβdiversity,with turnover and replacement components dominating over nestedness and richness difference components.The results of the Mantel test analysis showed that altitude was the main factor affectingβdiversity and its turnover.5.Current and future simulations using the Max Ent model to identify suitable distribution areas for two endemic fish species in the Hexi River system demonstrated that annual precipitation,slope and altitude were the three most influential environmental factors predicting suitable habitats for Gymnocypris chilianensis and Triplophysa hsutschouensis.The areas of suitable habitat for both species experienced a sequential westward decrease from the Shiyang River towards the Heihe and Shule Rivers under current climate conditions.Under future climate changes,the areas of the potential geographical distribution of G.chilianensis and T.hsutschouensis were concentrated eastward towards the Shiyang River and towards high-altitude regions in the southeast.This range shift was predicted to be more pronounced for G.chilianensis than for T.hsutschouensis.This study constructed a comprehensive species taxonomic checklist for fish in the Qilian Mountains.Our results demonstrate that riverine connectivity resulting from historical processes plays a vital role in shaping the freshwater ichthyofauna of High Central Asia,such as the Qilian Mountains.Both human influences（e.g.,construction dams）and biotic interactions（e.g.,biological invasions）are important factors driving the fish faunal structure among the six basins of the Qilian Mountains.Compared with human activities,environmental factors play a more dominant role in shaping fish diversity in the Qilian Mountains.Theβdiversity pattern was dominated by species turnover or replacement components,highlighting the need for conservation strategies that consider multiple species and areas to ensure sustainability.Future climate change poses severe threats to the potential habitat distribution of two endemic fish species;therefore,the effects of climate change must be incorporated into the integrated conservation plans for fish species in the Qilian Mountains and its adjacent areas.Our findings provide basic information for conserving and scientifically managing fish diversity in the Qilian Mountains.Scientific support for biodiversity monitoring and assessment and a data reference for ecological conservation and environmental safety research in the Qilian Mountains and the QTP also be offered.