| Plant can survive and reproduce in heterogeneous habitats via phenotypic variation and phenotypic plasticity.Classical theory holds that the major source of phenotypic diversity is genetic variation based on DNA sequence,but now this traditional opinion has been challenged by the recent studies arguing that the epigenetic variation influenced DNA methylation has the potential to influence the plant traits independently from genetic variation.To reveal the geographical and ecological patterns of epigenetic variation in natural plant populations,we surveyed the wild populations of Chinese chastetree(Vitex negundo var.heterophylla)in seven mountain areas(Dafotou,Liantaishan,Taishan,Menglianggu,Yaoxiang,Fanggan and Mengshan)from Shandong province of North China.For each site,we sampled individuals in understory and open habitats respectively.We recorded the longitude and latitude for each population and measured the plant height,basal diameter,number of resprouts and leaf traits for each sample.The genetic variation was detected with amplified fragment length polymorphism(AFLP)to analysed the genetic diversity and structure,and the epigenetic variation was observed by methylation-sensitive AFLP(MSAP)to calculate the epigenetic diversity and structure.The main results and conclusions of our research are listed as follow:(1)High levels of genetic and epigenetic were discovered in the 14 populations of V.negundo var.heterophylla from two contrary habitats.Among populations from all seven regions,the populations from Yaoxiang had the highest level of both genetic and epigenetic diversity,thus we suggested Yaoxiang as the key region for protection and development of germplasm resource.(2)The results showed that there was significant differentiation in plant functional traits between population from two different habitats,but molecular variance analysis(AMOVA)displayed that most genetic and epigenetic variation existed among regions and within populations while very little between habitats.Unexpectedly,bayesian clustering revealed a remarkable habitat-related genetic difference,and generalized linear models(GLM)determined more genetic loci associated with habitat type than epigenetic.Moreover,multiple matrix regression with randomization(MMRR)found the significant correlation between habitat and genetic variation.All above evidences supports that the adaptation to the habitat was genetically based and indicates a potential of independently parallel micro-evolution in this shrub.(3)Using Mantel tests and MMRR with the matrices of geographical,genetic and epigenetic distance,we found that the geographical distance was significantly correlated to both genetic and epigenetic distance.At the level of population,we found a higher geographic regression slope for genetic structure than epigenetic structure.The result implies that geographical isolation plays a significant role in shaping genetic structure,but it can affect epigenetic structure much restrictedly.(4)According the results of Mantel tests and MMRR among phenotypic,genetic and epigenetic variation,the correlation between genetic and epigenetic variation was very significant,the correlation between epigenetic and phenotypic variation was also significant,but there is no any significant relationship between genetic and phenotypic variation.These results suggest that epigenetic variation more contributes to phenotypic diversity than genetic variation,and that epigenetic variation is able to work as an independent factor from genetic control involving in phenotypic adaptation of plant to heterogeneous micro-habitats.In this study,we investigated the phenotypic,genetic and epigenetic diversity of natural population of V.negundo var.heterophylla in two different habitats from seven regions.The study has provided an insight into the relationship between epigenetic variation and ecological divergence in natural plant population,and could help the suggestions for ecological protection,vegetation restoration and germplasm conservation in North China. |
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