Phylogeography Of The Endangered Species Ulmus Lamellosa (Ulmaceae)

Ulmus lamellosa(Ulmaceae)is a deciduous and woody plant.It is an endangered and endemic species mainly distributed in China.Its key fruits contain high oil content(20-40%)and are an important food source for many insects and birds.Owing to the abundant decylic acid in seed,this species is an important light industrial raw material.And U.lamellosa has an important economic and ecological value.In recent years,the number of populations and individuals of U.lamellosa has dropped considerably owing to over-exploitation;it is now one of the Endangered Plant Species of Shanxi China.In this study,a total of 232 individuals were collected from fourteen populations of U.lamellosa,covering most of its entire distribution range in North China.We would investigate the phylogeographic history of U.lamellosa by using combined DNA sequences(cpDNA,trnD-trnE,psbA-trnH,atp B-rbc L and matK sequences;nrDNA ITS;single-copy nuclear gene Aat)and paleodistribution modeling approach.The genetic diversity,population structure,evolution process and population demographic history of U.lamellosa with the Ecological Niche Modeling(ENM)would be interpreted.And understanding the population demographic history and molecular phylogeography of this species is useful to design the suitable conservation planning.The main results as following:1 Chloroplast DNA analysisThe concatenated cpDNA sequences(trnD-trnE,psbA-trnH,atpB-rbc L and matK)had a total length of 2299 bp,in which 51 sites were variable.Ten haplotypes were identified in the combined cpDNA sequences data.High genetic diversity in U.lamellosa populations was detected(h T = 0.811,VT = 0.798,VS = 0.506)and a strong genetic structure(NST = 0.903 > GST = 0.639,P < 0.05)were found.The haplotypes Network analysis revealed that H3 was in the central position of the network and contained a higher frequency,given that it is a common and widespread haplotype.The mismatch distributions analysis revealed that U.lamellosa experienced a demographic expansion in the south region(Group I)and the demographic expansion occurred in approximately 0.101 Ma.The intraspecific divergence of all U.lamellosa cpDNA haplotypes most probably began in the late Miocene(9.27 Ma).2 nrDNA ITS analysisBased on nrDNA ITS sequences,18 haplotypes were identified.At the species level,high level of haplotype diversity and nucleotide diversity in U.lamellosa populations were detected(Hd = 0.424,? = 0.00212).The haplotype 1(H1)was shared in U.lamellosa populations except population LS.And H1 was in the central position of the network and contained a higher frequency,given that it is a common and widespread haplotype.The maximum likelihood tree of 18 ITS haplotypes clustered into three major clades,which was according to the geographic distribution.3 Single-copy nuclear gene Aat analysisAccording to single-copy nuclear gene Aat,23 haplotypes were identified.At the species level,high level of haplotype diversity and nucleotide diversity in U.lamellosa populations were detected(Hd = 0.941,? = 0.01601).And a strong genetic structure(NST = 0.738 > GST = 0.192,P < 0.05)were found in the studied.23 haplotypes clustered into three major clades,which consistent with the result of the maximum parsimony tree of haplotypes.4 Ecological niche modelling(ENM)All 34 distribution records of U.lamellosa were included in the ENM analysis,which suggested that the LGM distributions were slightly smaller than that of the present day,owing to the intensity of global cooling in the LGM.During the LIG,the potential range of this species was larger than that at present.This result was consistent with the result of cpDNA sequences that U.lamellosa experienced a minor local expansion(Group I)during the LIG and the demographic expansion occurred in approximately 0.101 Ma.In summary,high genetic diversity in U.lamellosa populations was detected and a strong genetic structure was found in the studied.U.lamellosa experienced a minor local expansion during the LIG.No evidence was found for long-distance southward migration or large-scale range contraction during glaciations and multiple refugia may have been maintained in mountains of North China.The endangered of U.lamellosa has nothing to do with genetic recession,but due to environmental change and human disturbance.