| As a hotspot of biodiversity,subtropical China harbors many tertiary relic plants.However,with the impacts of global warming and human activities,the survival of some ancient and rare plants has been threatened even towards extinction.Therefore,it is particularly important to study the habitats and genetic diversity of endangered plants for their protection.In this paper,genetic diversity and suitable distribution of an endangered gymnosperm Pseudolarix amabilis(Nelson)Rehd.(Pinaceae)in subtropical China,was studied by using 10 low-copy nuclear genes and niche modeling.The results of this study are the following:(1)Nucleotide diversity analysis of natural population and introduced cultivation populations of P.amabilis.The average genetic diversity of 23 P.amabilis populations distributed in China is relatively low(?=0.00308,?w=0.00456,Hd=0.4075,HE=0.032;?(s)=0.00343,?(s)=0.00328).Artificial introduced cultivation has an important contribution to maintaining genetic diversity.The genetic diversity of natural and cultivated populations is comparable(Natural:?=0.0018,Hd=0.2617,Ae=1.271,HE=0.04,and Shannon's index was 0.258;Cultivated:?=0.00169,Hd=0.2720,Ae=1.245,HE=0.03and Shannon's index was 0.23).Further analyses of the genetic components of cultivated populations implied that population SLC could be an important source for cultivation.PCA and Structure analyses showed that the natural population of P.amabilis could be clustered into four groups with different genetic components,(two west groups,ZRF and QPZ,one central SLC group,and an eastern group containing,group4).AMOVA results showed that the four groups had significant genetic differentiation(Fst=0.5045*).The western population has the lowest genetic diversity and a high degree of genetic differentiation.The eastern population has high genetic diversity and a low degree of genetic differentiation.Mismatch analysis showed that eastern population experience rapid population expansion events.Isolation by distance and isolation by environment analyses indicated the high differentiation of P.amabilis could be associated with both genetic drift within populations and local adaptation.(2)Suitable distribution based on niche modelingChanges in distribution of P.amabilis throughout different geological times(Last Interglacial,LIG,Last Glacial Maximum,LGM,Mid-Holocene,MH,current and future)have been investigated by means of niche modelling.The results showed that the main bioclimatic factors affecting the distribution of P.amabilis are bio17 and bio14.The bio2 is a key temperature factor across multiple periods and the annual average temperature affects the distribution in the current and future periods.The core distribution area of P.amabilis from the past to the future is relatively stable,mainly distributed in the mountainous regions such as Zhejiang,Anhui,Jiangxi,and Hunan,which can be partitioned into Eastern and Western parts.The suitable distribution of Western part was more affected by climate change and thus was severely fragemented.This may be responsible for low genetic diversity and high differentiation in western populations.The suitable distribution in the Eastern part is relatively stable and less affected by climate change,which could have promoted gene flow among population,resulting in a lower degree of genetic differentiation.According to the pattern of genetic diversity and the core suitable distribution across five periods,we can postulate that the mountains of south Anhui Province,Tianmushan Mountain in Zhejiang Province,Hengshan of Hunan Province and Dalongshan of Tonggu County of Jiangxi Province could be the glacial refugia for P.amabilis.This study elaborates the genetic diversity and genetic structure of P.amabilis based on ten nuclear loci and illustrate the potential distribution across different geological periods based on niche modelling.The results of this study provides an important theoretical basis for the protection of this rare and ancient plant. |
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