Effects Of Urbanization Landscape On The Spatial Distribution And Genetic Differentiation Of The Eastern Golden Frog(Pelophylax Plancyi)

City is a microcosm of the various changes happening globally,and urbanization is developing rapidly worldwise.The conflict between the land use changes caused by urbanization expansion and the request of natural habitats by wildlife species poses a severe threat to the biodiversity conservation in urbanized areas.The transformation of the landscape during urbanization leads to habitat fragmentation and loss,resulting in a continuing decline in habitat suitability and fragmented spatial distribution of wildlife populations.The impervious landcover in cities hinders individual dispersal and genetic exchange among populations,creates isolated local populations and differentiated population genetic structures,which are highly detrimental to the maintenance and long-term survival of wildlife populations in urbanized areas.Studying the spatial distribution patterns of urban wildlife populations and exploring how landscape connectivity affects gene exchange among small local populations can help us evaluate the survival status of wildlife populations,gain a further understanding of the impacts of urbanization on wildlife survival and evolution,and provide scientific guidance and suggestions for the protection of wildlife and their habitats in the urbanized area.Amphibians are characterized by high environmental sensitivity and restricted dispersal capability,making them one of the most threatened vertebrate groups,but also an ideal ecological indicator species.Shanghai,which is experiencing rapid urbanization,was selected as the research area,and Pelophylax plancyi was used as the research target species to explore the impact of urbanization on its spatial distribution pattern and population genetic differentiation.The occurrence records of P.plancyi were investigated using a line transect sampling technique,and biological tissue samples were collected for molecular biological analysis.Based on Landsat-8OLI＿TIRS satellite images,the landscape environmental data[land use type,normalized difference vegetation index（NDVI）,land surface temperature]were acquired.We used Max Ent to predict the potential spatial distribution pattern of P.plancyi in Shanghai and evaluate the habitat suitability.The software Circuitscape was employed to calculate the resistance distances between small local populations and evaluate the potential corridors.The genetic differentiation among populations was calculated based on simple sequence repeat（SSR）and single nucleotide polymorphism（SNP）molecular markers.The effects of the Euclidean distance and resistance distance on population genetic differentiation were explored by the Mantel test.The main results are listed as follows.（1）Among the land use types in Shanghai,the proportion of impervious surfaces was the highest（31.65%）.The urban area had the highest percentage of impervious surfaces,followed in order by the suburban area and the rural area.The urban area had the maximum land surface temperature（43℃）,followed in order by the suburban and rural area.The rural area had the highest NDVI,followed the order of decreasing by the suburban and urban areas.The concentric-ring expansion from the central urban outward established the urban-suburban-rural urbanization gradient in Shanghai.（2）The average AUC value of the Max Ent was 0.911±0.006,indicating excellent predictive performance.The Jackknife analysis showed that when using a single variable NDVI to build the model,the training gain was the highest（0.924±0.080）,followed by the land use type（0.904±0.058）and land surface temperature was the lowest（0.887±0.023）.The occurrence probability of P.plancyi in Shanghai increased with increasing NDVI values.As the increase of land surface temperature,the likelihood of occurrence was initially increased and peaked at around 35℃,then decreased.Regarding the land use type,forest and green land had the highest prediction probability.There was a significant negative relationship between habitat suitability and urbanization in P.plancyi（R=-0.610,P=0.016）.（3）There was no significant correlation observed between the Euclidean distance and the genetic distance calculated by SSR data(F_ST,SSR:R=0.030,P=0.162;F_ST/(1-F_ST)_SSR:R=0.031,P=0.163)or between the Euclidean distance and the genetic distance calculated by SNP data(F_ST,SNP:R=0.005,P=0.347;F_ST/(1-F_ST)_SNP:R=0.005,P=0.343).However,there was a significant positive correlation between the resistance distance and the genetic distance(F_ST,_SSR:R=0.593,P<0.001;F_ST/(1-F_ST)_SSR:R=0.598,P<0.001;F_ST,SNP:R=0.420,P=0.006;F_ST/(1-F_ST)_SNP:R=0.419,P=0.006).As the resistance distance increased,so did the level of genetic differentiation.In conclusion,the rapid urbanization development in Shanghai City has altered the land use types significantly,and induced loss and fragmentation of habitat,affected the spatial distribution pattern of P.plancyi.The heavy urbanization has also reduced the landscape connectivity between the habitats,hindering individual dispersal and gene flow,then posing a threat to its long-term survival.Therefore,for amphibian species with limited dispersal ability and high sensitivity to environmental changes,the primary measure to maintain their local populations in urban areas is to preserve and maintain their fragmented habitat patches in urban areas and their still remnant connected habitat in the suburban areas,which is also essential step for long-term biodiversity conservation in urbanized areas.Furthermore,optimizing the urban landscape structure,establishing ecological corridor networks suitable for various wildlife groups,increasing connectivity between habitats,and promoting gene exchange among small local populations are important measures for the sustainment of populations and long-term conservation of wildlife biodiversity in urbanized areas.