| Urbanization is one of the most serious threats to global ecosystem.With the rapid development of current urbanization,urban biodiversity is under great threat in China.Urban plants are usually at the bottom of the food chain of urban ecosystem,and the diversity of urban plants has an important impact on the diversity of other urban organisms.Therefore,it is necessary to start studying the impact of urbanization on the diversity of urban plants,especially genetic diversity,which is an important component of biodiversity.Pteris multifida Poir,the object of this study,which was a fern widely grown in urban areas.Based on Super GBS to obtain single nucleotide polymorphisms(SNP),we used proportion of building area,proportion of impervious surface and population density within the radius of 1 km and 3 km as indicators of urbanization.We explored the effects of urbanization and landscape changes on the genetic diversity of P.multifida,simulated the impact of future urbanization on the genetic structure of the populations of P.multifida,and detected outlier associated with urbanization.The main results are as follows:(1)Urbanization could reduce the genetic diversity of P.multifida.The populations in low urbanized region have higher genetic diversity than those in moderate and high urbanized regions.All proportion of building area,proportion of impervious surface,population density and landscape indices related to construction land were negatively correlated to the genetic diversity indexes.Proportion of building area,proportion of impervious surface and landscape indices related to construction land were negatively significantly correlated to genetic diversity indexes,while population density was not significant at the 0.05 level.Proportion of building area(1 km)was taken as an example,it was negatively significantly correlated to Ne(r =-0.881,p = 0.001),I(r=-0.861,p = 0.001),He(r =-0.874,p = 0.001)and so on.(2)Urbanization could affect the genetic divergence of P.multifida.The Fst of P.multifida was 0.048(p = 0.001),which implied low genetic divergence.All proportion of impervious surface,the landscape indices related to construction land and agricultural land were significantly correlated to genetic divergence of the populations of P.multifida,while population density was not significantly correlated to genetic divergence.Both proportion of building area and the landscape indice related to grassland were significantly correlated to genetic divergence at a certain scale.Proportion of building area(1 km)was taken as an example,it was significantly correlated to Fst(r=-0.547,p = 0.030).(3)Urbanization had an important effect on the genetic structure of the populations of P.multifida.PCA apparently distinguished low urbanization populations from both moderate and high urbanization populations,but could not distinguish moderate and high urbanization populations.AMOVA result showed the highest proportion of genetic variation and genetic divergence between low and high urbanization populations.Structure analyses showed that there were two gene pools in the populations of P.multifida,and low urbanization populations contained dominant individuals in both two gene pools,while moderate and high urbanization populations only had dominant individuals in one gene pool.POPS showed,when K = 2,the development of urbanization in the future might lead the populations of P.multifida tend to aggregate into one group.(4)Urbanization had a selective effect on the genome of P.multifida.Among18,359 SNP markers,there were 104 outliers associated with urbanization indicators,12 outliers associated with proportion of building area,6 outliers associated with proportion of impervious surface,and 98 outliers associated with population density.In short,urbanization could affect the genetic diversity and structure of P.multifida,which might reduce the genetic diversity of P.multifida,affect genetic divergence and genetic structure,and increase the selection effect of P.multifida.This study provided a reference for further studies on the effects of urbanization on the genetic diversity of urban plants. |
