Landscape Genetics Of Sassafras Tzumu Based On The Genotyping-by-Sequencing(GBS)

Sassafras tzumu Hemsl.belongs to the family Lauraceae.It is mainly distributed in mainland China and North America,and its materials are widely used.At present,research on S.tzumu focuses on exploring its physiological and biochemical characteristics.As a species widely distributed in the south of the Yangtze River,using S.tzumu as a representative,using the distribution information of S.tzumu to study the distribution of species in these areas and predicting its response to climate change has important significance for species protection.In addition,combined with genotypingby-sequencing technology and landscape genetics research,it is possible to reveal the relationship between the genetic structure and the geographical distribution of its representative groups,to analyze the effects of different evolutionary forces on species,and to use this correlation to predict the genetic structure and genetic diversity of species with future climate change.This study investigated the genetic diversity and landscape genetics of S.tzumu by the results of GBS simplified genome sequencing of a total of 106 individuals in 13 populations.Biomod2 combined model was used to simulate the distribution of S.tzumu.The AUC value of the combined model was greater than 0.89,which was a very good prediction.Bioclimatic factors affecting their distribution are Mean Diurnal Range(Bio02),Annual Mean Temperature(Bio01),Temperature Seasonality(Bio04)and Precipitation of Driest Month(Bio14).The model results show that S.tzumu is mainly distributed in most areas south of the Yangtze River,west to Sichuan province,east to Jiangsu province,north to Qinling Mountains-Huaihe River Line and south to Taiwan under the baseline climate conditions.The area suitable for distribution is 1740100 square kilometers,accounting for 18.1% of China's territorial area.Climate change will affect the distribution of S.tzumu.Specifically,the area of suitable land tends to decrease in general,and will be inversely proportional to the increase of carbon emissions.The centroid of the distribution area shifted to the North obviously.Analysis of genetic diversity of 11862 single nucleotide polymorphic loci obtained by sequencing.The results showed that the expected heterozygosity(He)was 0.3004,the observed heterozygosity(Ho)was 0.2604,and the polymorphic information content(PIC)was 0.2457.The effective allele content(Ne)was 1.4897.Nucleotide diversity(Pi)was 0.3019.Principal component analysis results of S.tzumu showed that SS,ML,LS and HS came together,the others came together.The phylogenetic tree results PCA analysis results.Structure results showed that S.tzumu came from two gene pools.BayeScan was used to identify the SNP in the S.tzumu,and a total of 104 Outliers were obtained.Among the 104 Outliers,the LFMM algorithm in the R-language "LEA" package was used to detect the environment-related location.The test results showed that 53 of them were related to the environment.Among the 53 sites,the most related to Bio03.The environmental related locus results of S.tzumu showed that Bio03 had a greater impact on the genetic structure of S.tzumu.POPs results show that Cluster 4 and Cluster 1 tend to move southwestward with climate change,while Cluster 2 has more preponderance under climate change.Canoco 5 was used to calculate the influence of environmental factors on genetic data.The results showed that the environmental factors which had great influence on genetic data were Isothermality,Coefficient of variation of Precipitation seasonality,Temperature seasonality,Precipitation of wettest month,Mean annual temperature and Mean diurnal range,and their P values were less than 0.05.This is consistent with the LFMM results.The results of Multiple Matrix Regression with Randomization analysis(MMRR)showed that the spatial genetic differentiation of S.tzumu had significant IBD and IBE effects.IBE=1.54 IBD,IBE has a more significant effect than IBD,that is,IBE can better reveal its genetic differentiation.In addition,the ZT results showed that the annual average temperature also affected the genetic distance.