Genetic Diversity And Differentiation Between Island And Inland Populations Of Bryum Argenteum

Bryum argenteum Hedw.is a widespread species,which is easy to be identified and collected.It is an ideal material for comparing the genetic differentiation between island and inland moss populations.In this study,The genetic diversity of Bryum argenteum were studied based on its 298 samples from fifteen inland and forty island populations by using Inter-Simple Sequence Repeat?ISSR?markers to reveal the level of genetic diversity and the genetic structure of the populations and to explore the reasons.In addition,the genetic structure,the level of genetic diversity and the characteristics of genetic differentiation of islands and inland Bryum argenteum populations were compared and the relationship between environmental factors and genetic diversity of Bryum argenteum populations in islands was explored.The aim was to reveal the effects of isolated environment on the genetic diversity and differentiation of bryophytes,and to explore the environmental factors affecting the genetic structure of bryophytes,so as to enrich people's understanding of the impact of island environment on the diversity of bryophytes.The main research results are as follows:?1?ISSR-PCR system of Bryum argenteum was optimized by orthogonal experimental design.The system volume was chose as 20 ?L after comparing the influence of different system valume on PCR results.The optimized system for Bryum argenteum ISSR-PCR analysis contained 2 ?L 10 × LA PCR Buffer II(Mg²⁺ free),20 ng DNA template,0.45 ?mol/L primer,2.65 mmol/L Mg²⁺,0.4 U Taq DNA polymerase,and 0.45 mmol/L d NTPs.A total of fifty primers for ISSR-PCR of Bryum argenteum were selected.An optimal annealing temperature of each primer was determined by using a temperature gradient PCR.?2?By using inter-simple sequence repeat?ISSR?markers to determine the genetic diversity and genetic differentiation of 55 populations of Bryum argenteum from islands and inland.A total of 623 discernible loci were obtained using 20 primers,the percentage of polymorphic loci?PPL?was estimated up to 90.05%.As analyzed by POPGEN,Nei's genetic diversity?Ht = 0.2403?,Shannon information index?Hsp = 0.3835?,and Genetic diversity within populations?Hs = 0.1231?indicated that Bryum argenteum had a high level of genetic diversity.48.68% genetic variation exited among the different populations and 51.23% genetic variation exited within populations.The gene flow?Nm?between populations was low.There also existed distinctive geographical influence on genetic differentiation?r = 0.171,P < 0.005?.The results showed that geographic isolation and genetic drift are important factors for the genetic differentiation of 55 Bryum argenteum populations in this paper.?3?By comparing the genetic diversity levels of island and inland Bryum argenteum populations,it was found that Nei's genetic diversity?Ht = 0.2396?,Shannon information index?Hsp = 0.3804?,and Genetic diversity within populations?Hs = 0.1339?of island populations were all higher than those of island populations?Ht = 0.2329,Hsp = 0.3698,Hs = 0.1190?.There was no significant difference in genetic diversity between island and inland populations.Environmental heterogeneity,population size and human activities had important effects on the level of genetic diversity of the population of Bryum argenteum.?4?In this study,the coefficient of population differentiation of the island populations?Gst = 0.4891?was greater than that of the inland populations?Gst = 0.4412?,and the gene flow between the island populations?Nm = 0.5362?was lower than that between the inland populations?Nm = 0.6357?.Within the island,only about 30.67%-28.48% of genetic diversity was caused by the difference between populations,while the genetic differentiation degree of inter-island populations was as high as 48.91%.It was suggested that the isolation effect of islands is mainly manifested in the inhibition of gene exchange among the island populations.Insular geographical isolation had great influences and significant correlation was found between genetic distance and insular geographic distance?r = 0.19,P < 0.01?.?5?The correlation between the genetic diversity of Bryum argenteum populations and the environmental factors of the islands showed that the genetic diversity of the islands populations was significantly correlated with the vegetation coverage,building density,island altitude,coastline,area and population of the islands.In addition,through the fitting curve of environmental factors and Nei's gene diversity,it was found that the island altitude and area,as well as a certain degree of human activities,played an important role in maintaining the genetic diversity level of the populations of the Bryum argenteum in islands.