Phylogeography Of Actinidia Eriantha In Evergreen Broad-Leaved Forest Of Subtropical China

Subtropical evergreen broad-leaved forest（EBLF）represents the typical vegetation in subtropical China and has been used to explore how associated forest elements respond to past environmental change in recent years.As an important component of subtropical forest ecosystem,lianas usually have a large impact on restoration and succession of the communities of EBLF.However,most phylogeographic studies have focused on evergreen trees,with few studies using liana species.Here,we chose a typical understory woody deciduous liana Actinidia eriantha that occurs across the eastern moist EBLF for phylogeographic study.Actinidia eriantha Benth.is a diploid perennial woody vine native to China and is recognized as a valuable species for commercial kiwifruit improvement with high levels of ascorbic acid as well as having been used in traditional Chinese medicine.We used three chloroplast DNA loci and 38 nuclear microsatellite loci,a combination of traditional phylogenetic and population genetic approaches,and powerful novel statistic methods such as Species Distribution Models（SDM）to explore the patterns of genetic diversity and population divergence,the effects of paleoclimatic oscillations and vicariance,the model best explaining the response to climate fluctuations,and the possible refugia and expansion routes of A.eriantha.Due to the lack of genomic resources for the species,microsatellite markers for population genetics studies are scarce.In this study,RNASeq was conducted on fruit tissue of A.eriantha,yielding 5,678,129 reads with a total output of 3.41 Gb.De novo assembly yielded 69,783non-redundant unigenes（41.3 Mb）,of which 21,730 were annotated using protein databases.A total of 8,658 EST-SSR loci were identified in 7,495 unigene sequences,for which primer pairs were successfully designed for 3,842 loci（44.4%）.Among these,183 primer pairs were assayed for PCR amplification,yielding 69 with detectable polymorphism in A.eriantha.Additionally,61of the 69 polymorphic loci could be successfully amplified in at least one other Actinidia species.We randomly chose 32 EST-SSR of A.eriantha and 6 screened from A.chinensis.Average estimates of genetic diversity at the population level（Ae=2.52;H_E=0.510）may be underestimated due to the usage of EST-SSR markers and was actually relatively high.Actinidia eriantha showed a relatively low level of population differentiation(F_ST=0.177),which may result from high levels of gene flow.High levels of gene flow among populations can be explained as a result of effective seed dispersal.Microsatellite markers revealed five clusters largely corresponding to geographic regions.Coalescent time of cp DNA lineages was dated to the middle Pliocene（ca.4.03 Ma）.Phylogeographic analysis and species distribution modelling revealed that A.eriantha originated from the southern Fujian Hilly Region and expanded repeatedly from and contracted into the Wuyi Mountains during different glacial periods.Dispersal corridor analysis revealed an east-west colonization route in subtropical China.In addition,geographic distance had a significant impact on current genetic differentiation between populations.There is no significant correlation between environment distance and intraspecific genetic divergence,indicating a conserved ecological niche.Our study supports an expansion-contraction model and suggests that climatic fluctuations,vicariance and intrinsic factors all contributed to historical demography and the current population structure in A.eriantha and provide a new insight into the phylogeography of liana plant in EBLF.