| The existing distribution pattern of biodiversity is influenced by the interaction of long-term biological and abiotic environment.However,abiotic environment plays a key role in the formation of biodiversity.The karst area in southwest China(mainly in Guangxi Zhuang Autonomous Region,Yunnan Province and Guizhou Province)is the largest karst distribution area in the word,and it also distribute in one of the 34 biodiversity hotspots in worldwide.Previous studies have shown that there were some differences on plant composition and biodiversity between karst and non karst areas in southeast of China and karst landform plays an important role in the formation of flora in there.The impact of environmental factors on the biodiversity of regional wildlife has been widely studied,but it mainly focuses on temperature,precipitation,altitude and so on.However,there are few researches on the influence of topography and geomorphology on the geographical distribution pattern of wildlife diversity,while the influence of karst geomorphology on the geographical distribution pattern of regional wildlife diversity is still lackingOur present research focuses on the distribution of amphibians in typical karst region in southwest China(mainly in Guangxi Zhuang Autonomous Region,Yunnan Province and Guizhou Province).The distribution of amphibians in the karst and non-karst regions were surveyed,and we also collected the historical data from the Chengdu Institute of Biology,Chinese Academy of Sciences,Herbarium of Kunming Institute of Zoology,Chinese Academy of Sciences,Natural Museum of Guangxi Zhuang Autonomous Region,and Herbarium of Central South University of Forestry and Technology,as well as the data in public literature to constitute the amphibian database of southwest karst landform.Using these data,the composition,distribution,and difference in species richness between karst and non-karst regions were analyzed.Based on the current climate,altitude,vegetation type and other data,the maximum entropy(MaxEnt)model was used to estimate the potential distribution area of amphibian species.Then,the environmental factors and formation mechanism that affect the distribution pattern of amphibian species richness in karst area and non karst area are furture studied.Finally,the future climate change on the influence of amphibians between the karst area and non karst area was investigated.This study will have a deeper understanding of the formation mechanism of amphibian geographical distribution pattern,such as climate,landform(karst landform and non karst landform),which is of great significance to the protection of amphibian and even biodiversity in this area,and also provides a certain reference for the scientific protection work of amphibian in this area.Our main findings are as follows:(1)We obtained the data of amphibian distribution in karst landform area of Southwest China.Based on the field investigation and collection of data from the relevant Herbarium,219 species of amphibians are recorded in this area,belonging to3 orders,12 families and 48 genera,accounting for 46.50%of the total 471 known amphibian species in China.Among them,the order with the largest number of species is Anura,191 species,accounting for 87.21%of the total number of species;then the Caudata,27 species,accounting for 12.33%;and the lumbricoides,1 species,accounting for 0.46%.There are 10 species of amphibians only distributed in karst area,accounting for 4.57%of the total species;104 species of amphibians only distributed in non karst area,accounting for 47.49%of the total species;105 species of amphibians are distributed in both karst area and non karst area,accounting for47.94%of the total species.(2)There are significant differences in amphibian diversity between karst and non karst areas in Southwest China.The non-parametric Mann-Whitney U test showed tha there was no significant difference among families(U=3.0,z=-1.080,P=0.032)and among G index(U=3.0,z=-1.061,P=0.289),while there was significant difference among genera(U=0,z=-2.141,P=0.032),among species richness(U=0,z=-2.141,P=0.032),among F index(U=0,z=-2.121,P=0.034),and among G-F index(U=0,z=-2.121,P=0.034).In addition,there is no significant difference in the ecological type(except for the terrestrial hydrostatic type)and fauna distribution between the karst and non karst areas.(3)Combining with the current climate,altitude,vegetation type and other data,the maximum entropy(MaxEnt)model is used to estimate the potential distribution area of amphibian species.Firstly,the potential distribution area of each amphibian species is estimated,and then the potential distribution area of each species is superposed to generate the potential distribution map of this study area.The results show that the average AUC values of the training data set and the test data set estimated by the model are greater than 0.88,which shows that the model distribution prediction has achieved good fits.Secondly,the analysis of the distribution pattern of species richness shows that the places with the highest amphibian species richness are mainly located in non karst areas,i.e.near Dayaoshan National Nature Reserve in Guangxi,and the places with the highest amphibian species richness in karst areas are mainly located near nongang National Nature Reserve in Guangxi.(4)The formation ofthe geographical distribution pattern of amphibian species richness in this area is the result of the interaction of various factors.In order to explore the factors influencing the formation of amphibian species richness distribution pattern in the region,30 environmental factors such as high-resolution climate,topography and vegetation representing energy hypothesis,water hypothesis,productivity hypothesis and habitat heterogeneity hypothesis were analyzed.Firstly,the results show that the influence of latitude and longitude on the distribution pattern of amphibian species richness is very small(R~2<0.05).Further analysis shows that the largest environmental factor of amphibian species richness distribution pattern in this area is the annual rainfall in the water hypothesis(R~2=0.232,P<0.001),followed by the average rainfall in the driest month(R~2=0.221,P<0.001).Finally,based on the model selection analysis,the mixed model(including all environmental factors)is the best model to explain the species richness pattern of amphibians,which can explain42.5%of the spatial variation of the richness.It can be seen that different ecological hypotheses or multiple environmental factors are not mutually exclusive,but together affect the species richness pattern of amphibians.(5)In the future,climate change will lead to the increase of amphibian abundance in karst and non karst areas,showing a trend of higher species richness with lower latitude.Using the new scenario data of global greenhouse gas concentration and climate change released by the fifth assessment report of the Intergovernmental Panel climate change(IPCC),we used the maximum entropy(MaxEnt)model to estimate the distribution of amphibians in the study area in 2050and the pattern of species diversity under the representative concentration pathways(RCP)4.5.With the increase of rainfall and temperature in the future,the abundance of amphibians in karst and non karst landforms in the region increases significantly.Global climate change will be conducive to the spread of amphibians in the region.In a summary,we proposed that the karst landform,along with several environmental factors such as rainfall and temperature,concordantly affected the distribution pattern of amphibian in our research region.However,a considerable proportion of variation remains unexplained.Therefore,in order to fully understand the formation mechanism of amphibian species richness pattern in this region,it is necessary to strengthen the research on the influence of other biological factors such as interference,predation and competition. |
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