Elevational Patterns Of Species And Functional Diversity Of Aquatic Insects In The Lancang River,Yunnan Province

Community-level species diversity and functional diversity are sensitive to human disturbance and natural gradient.Elevational patterns of species diversity and functional diversity are affected by multiple ecological processes under different spatial scales,thus is an important aspect to understand the biodiversity maintenance and changes.Climatic variables and land use conversions are two main mechanistic factors would significantly impact the changes in species diversity and functional diversity along elevational gradients.Disentangling the effects of climate and land use on species diversity and functional diversity is essential to understand and predict the future impact of global change on biological communities.However,the spatial scale dependency of elevational patterns on species diversity and functional diversity of aquatic insect assemblages remains unclear.There is also a lack of understanding of the comprehensive impact of climate and land use on aquatic insect biodiversity.Using 149 stream data collected along elevational gradient ranging between 500-3,900 m during 2013 and 2018,I used random forest model to identify the key factors that influence species diversity and functional diversity.I then examined how elevational patterns of species diversity and functional diversity of aquatic insect assemblages differed across local and regional scales among multiple elevational bands by linear or quadratic regression models.Finally,I constructed generalized additive model to analyze climate and land use interactive effects on species diversity and functional diversity in aquatic insect.The main results I found are:(1)A total of 277 taxa were identified,belonging to 10 orders and 102 families.Of all taxa collected,Diptera,Coleoptera,Ephemeroptera and Trichoptera were predominant biological groups with greater richness.(2)Variation in species richness(40.7%),Simpson diversity(19.5%),evenness(21.1%),dendrogram-based functional diversity(dbFD)(43.8%),Rao's Q diversity(RaoQ)(20.1%),and functional evenness(FEve)(15.0%)among sites was associated with a combination of human disturbance and natural gradient.Species richness and dbFD are positively correlated with the percentage of forest land or the percentage of cobbles,and negatively correlated with annual mean temperature,temperature annual range,total nitrogen.Simpson diversity and RaoQ are positively correlated with the percentage of forest land,and negatively correlated with latitude or total phosphorus.Evenness positively correlated with annual mean precipitation,and negatively correlated with total nitrogen,and positively correlated with water temperature and chemical oxygen demand within a certain threshold.FEve show a flux that increase first then decrease with increasing temperature annual range,and positively correlated with the percentage of sand,annual mean temperature and water depth,and negatively correlated with stream width within 0-5m threshold.(3)At the local scale,species richness and dbFD show no significant elevational patterns;while Simpson diversity,RaoQ,evenness,and FEve show either U-shaped or monotonically decreasing trends along elevation gradients.At the regional scale with increasing elevation,species richness decreases(NS)while dbFD changes from U-shaped to a monotonically decreasing trend along the elevational gradient.Both Simpson diversity and RaoQ change from a significant U-shaped to no significant regional elevational patterns.Evenness and FEve have no significant relationship with and significantly increased with regional elevations,respectively.(4)The generalized additive model show that the climate-land use interaction models explained considerably more variation in species diversity and functional diversity indices than did simple additive effect models,or models with single predictor variables.Acorss all models,there is a significant difference between the response of functional diversity to the effects of climate and land use alone or combined with species diversity.These results implied that the functional diversity of aquatic insect community is an important component to evaluate the change of biodiversity changes under global human and natural environmental changes in the Lancang River Basin,Yunnan Province,and it is important for a comprehensive understanding of the climate and land use impacts on community assemblage.The results show that aquatic insect species diversity and functional diversity are sensitive to human disturbance and natural gradient.The aquatic insect species diversity and functional diversity are scale dependent across elevations.However,I observed a degree of consistency in elevational patterns for each species diversity and functional diversity indices across elevational bands at regional scales.The climate and land use effects on aquatic insect species diversity and functional diversity are not a single-factor mechanism,which have significant interactive effects on species communities.This study systematically analyzed the aquatic insect data in the Lancang River Basin in Yunnan province.Specifically,I analyzed the spatial distribution of species diversity and functional diversity in the study area,identified the main environmental factors that would influence species diversity and functional diversity,compared the elevational pattern of species diversity and functional diversity between local and regional scales,and quantified the relative role of climate and land use factors on the biodiversity indices,and disentangled the impact of climate and land use accumulation and interaction on the species diversity and functional diversity of aquatic insect.The results I found in this study are expected to improve our understanding on the response of biodiversity to environmental change,and strengthen the understanding of the spatial scale effect on the elevational pattern of biodiversity.It can also provide important data collection and knowledge basis to understand the current biodiversity condition and formulate biodiversity protection and conservation strategies in the Lancang River Basin.It can further provide data accumulation and research support to reveal and predict the impact of global change(i.e.,climate change and land use)on regional and global biodiversity.