Studies On Molecular Phylogeography Of Enkianthus Chinensis Complex

Enkianthus chinensiscomplex(Enkianthus)belongs to the Sect.Racemus of Enkianthus Lour.in the family Ericaceae,a beautiful ornamental plantand arepresentative of montane elfin forest in subtropical C hina.In this study,a chloroplast fragment(psb A-trn H intergenic spacer)of the Enk.chinensiscomplex(Enkianthus)was used to detect the genetic diversity and genetic structure,andthe potential distribution area s of Enk.chinensiscomplex(Enkianthus)in different historical periods were simulated using the ecological niche modeling(ENM),to explore the formation of distribution pattern and evolutionary history.The main results are as follows:(1)A total of 651 individuals from 48 populations of Enk.chinensiscomplex were collected in this study,among them 219 individuals in 40 populations used in this experiment.Twenty chloroplast haplotypes were identified in Enk.chinensiscomplex.Genetic diversity in the species complex was high(H_T=0.787).Significant phygeographical structurewas found in the species complex and its three component lineages.Mantel test indicated significant isolation-by-distance.The Eastern Himalayas,Hengduan Mountains,Daba Mountain,Wushan and Jinfo Mountain are likely to be the refigia for the species complex due to their highhaplotype or possessing unique haplotypes.These areas should be prioritized in the protection of the species complex as well as the montane elfin forest in subtropical China.(2)Three chloroplast lineages were identified,and these lineages(I,II,and III)successively diverged at ca.1.81 Ma(0.23-4.07Ma),1.79Ma(0.33-3.85Ma)and 1.81Ma(0.39-3.72Ma).Most of the haplotypes differentiated in the Middle Pleistocene.Demographic analyses find that size of total populationsand midwesternpopulations were relatively stable,eastern populationshave experienced expansion in the history,and the expansion events happened atca.20ka(Last Glacial Maximum).The expansion events may be related to cold eastern climate of last glacial maximum.The intraspecific diversification of Enk.chinensis complex could be affected by the most recent uplifted of Tibetan plateau,the intensification of the Asian monsoon climate and the Q uaternary ice age all work together.(3)The results of reconstruction of the ancestral distribution area indicated that Enk.chinensis complex could originate in the Daba Mountains-Wushan Mountains,then one lineage expanded westward to the Hengduan Mountains and Himalayas,and another expanded southeastward.The evolutionary history resulted in a clear pattern of differentiation in the east,middle and west.(4)Although there are some differences in morphology and habitat between the Enkianthus deflexus and Enkianthuschinensis,the chloroplast DNA sequence indicated that the two taxawere not reciprocally monophyletic.The morphological differences between the two species might be adaptive under different environments and Enk.deflexus and Enk.chinensisshould be merged into one species.(5)ENM results indicated that the suitable distribution of Enk.chinensis complex was divided into the east and the midwest parts.The suitable distribution area in the midwest was larger,and relatively stable(e xcept for the future),only the distribution of the Himalayas changes significantly in different periods.While the suitable distribution area in the east was relatively scattered and has changed greatly in different periods.Eastern populationshave experienced expansionduring thelastglacial maximum,particularlycontinental shelf of east china sea and bohai sea.In the future,the potential distribution of Enk.chinensis complex will decerase and experience severe fragmentization.All the mid-western Enk.chinensis complexes will migrate to high altitude areas,which is extremely unfavorable for t he survival of Enk.chinensis complex.Put together,the results of this study suggest that Daba Mountains-Wushan Mountains-Daluo Mountains is a phylogeographic break between the eastern and midwestern populations of Enk.chinensis complex.The results of this study suggest that the Quaternary climate changes have had profound impacts on the evolution of Enk.chinensis complex.The three lineages and gradual expansion revealed in this study would have important implications for the conservation of the species complex,as well as the montane elfin forest in subtropical China.