Influence Of Climatic Factors On Genetic Diversity And Genetic Structure Of Cleistogenes Squarrosa Keng At Large Scale Gradient

Genetic diversity is an important component of biodiversity,which is the basis for the species survival,development and evolution and plays a decisive role in species diversity and ecosystem diversity.The degree of genetic variation among populations and their distribution patterns form genetic structure,and genetic variation among plant populations often occurs along different climatic gradients,such as changes in temperature and precipitation.Recent studies have found evidence that reduced precipitation decreases genetic diversity,and while Cleistogenes squarrosa Keng is sensitive to climate change,and studies analyzing genetic adaptation mechanisms in grassland plants based on Cleistogenes squarrosa K.are still lacking.In this experiment,the genetic diversity and genetic structure of rbcl sequences,trn L-trn F sequences and their combined sequences were analysed,and the correlation between genetic distance,geographic distance and environmental distance among populations was calculated to investigate the effect of temperature and precipitation on genetic diversity and genetic structure of different populations and the genetic differentiation of Cleistogenes squarrosa K.at 20 sample sites.The results of this study can reveal the effects of large-scale gradients in precipitation and temperature on the genetic diversity and genetic structure of Cleistogenes squarrosa K.,and provide a theoretical basis for the genetic adaptation mechanisms of grassland plants in Inner Mongolia.The main results of this study are as follows.(1)The genetic diversity of all the Cleistogenes squarrosa K.obtained in this experiment was low.In terms of nucleotide polymorphism,the trn L-trn F sequence had the largest nucleotide polymorphism(π=0.00544),the rbcl sequence the second largest(π=0.00117)and the joint sequence the smallest(π=0.00096).In the haplotype diversity analysis,the rbcl sequence had the greatest haplotype diversity(vh=0.561)and the greatest number of haplotypes(n=19),the joint sequence was the next most diverse(vh=0.544,n=0.15)and the trn L-trn F sequence was the least diverse(vh=0.514,n=9).Genetic diversity was greatest for the joint sequence(HT=0.628)and least for the trn Ltrn F(HT=0.587).The genetic diversity of Cleistogenes squarrosa K.in the typical grassland zone is higher than that of Cleistogenes squarrosa K.in the desert grassland zone.,and AMOVA analysis showed that genetic variation occurred both among and within populations,but mainly among populations.Neutrality tests were negative,and mismatch distributions also showed that most populations were unimodal,suggesting that most populations of Cleistogenes squarrosa K.have undergone population expansion and are well adapted to their local environment.(2)The haplotype network diagrams of both rbcl sequences,trn L-trn F sequences and combined sequences could be divided into two categories.The results of the NJ and MP trees also show that the haplotypes were divided into two branches.Structure analysis explored the population perspective and found that the rbcl sequences did not clearly distinguish between genetic structures,but the results of both trn L-trn F sequences and combined sequences showed that the 20 populations could be divided into two clusters.Populations 1 to population 8 were divided into one cluster and located in desert grassland,and populations 9 to population 20 were divided into one cluster and located in typical grassland,demonstrating that the genetic structure of Cleistogenes squarrosa K is determined by the ecoclimatic zone.(3)The results of principal component analysis showed that the 19 climatic variables related to precipitation and temperature were well differentiated among the 20 populations.Mantel test showed that geographical distance was significantly correlated with genetic distance,while climatic distance was highly significantly correlated with genetic distance.The partial mantel test showed that genetic distance was significantly correlated with climatic distance when geographical distance was excluded.However,after excluding the effect of climatic distance,genetic distance was not correlated with geographical distance.Among the environmental factors,the correlation between genetic distance and annual precipitation was greater than the correlation between genetic distance and annual mean temperature.In general,the genetic distance between populations of Cleistogenes squarrosa K is more influenced by climatic factors,with precipitation having a higher impact than mean temperature.In summary,the genetic diversity and genetic structure of combined sequences were significantly correlated with the climate,and the higher the precipitation and temperature,the more significant the populations differentiation.