Genetic Diversity And Population Structure Of Quercus Chenii In The Urban Forests Of Wuhan

As an important part of natural resources and environment in urban ecosystem,urban forest plays an important role in improving urban ecological environment.However,with the process of urbanization,in the urban ecosystem,urban forests often appear as patches and islands.It is a typical area of habitat fragmentation.Urban forest patches will intensify the isolation of plant populations.increases the probability of inbreeding depression in small populations,lead to population structure is unstable.Ultimately,reduced biodiversity and ecosystem function.So,whether plants can maintain their genetic diversity and population structure through pollen flow and seeds flow in urban forests with severe habitat fragmentation will have a profound impact on the function of urban forest communities.As a large city in China,the forest fragmentation of Wuhan city is serious.The remaining forest patches in the central city area are small,and scattered in independent mountains in protected areas such as parks and universities.Quercus chenii,a genus of fagaceae,is endemic to China.In the mid to late 20th century,Quercus chenii was widely used in the restoration and afforestation in the central city of Wuhan.Now it has become the dominant tree species in these patches.The genetic characteristics of Quercus chenii population in Wuhan urban forest were studied by using microsatellite molecular markers.By comparing the genetic diversity and structure of seedlings and adult trees,the population structure and dynamics of Quercus chenii were analyzed by quadrat survey,The objective of the experiment was to investigate whether dominant tree species could achieve population self-maintenance and development in urban forests with high patchy and frequent human disturbance.The main results are as follows:Based on 6 pairs of nuclear SSR markers,the genetic diversity and genetic structure of 463 Quercus chenii seedlings and 154 parent trees in 8 patches in Wuhan were studied.It was found that Quercus chenii population in eight patches had a high level of genetic diversity(Na=17,Ne=3.806,I=1.529),and the genetic variation of seedlings and trees in Quercus chenii population mainly occurred in the population(90%).The intrapopulation variation of seedlings(97%)is higher than that of adults(92%).Principal component analysis and STRUCTURE analysis also proved that there was no obvious genetic difference among the eight Quercus chenii populations in both seedling stage and tree stage.In general,the gene flow of seedlings among populations(Nm=13.191)is greater than that of adult trees(Nm=7.892).These results showed that the isolation did not restrict the gene flow of Quercus chenii in the selected forest patches in Wuhan.This may be related to the wind-borne pollination of Quercus chenii and the long distance of pollen transmission,In addition,Quercus chenii,which has the ability to spread oak seeds over a long distance,may also provide the possibility for its seed flow.In order to investigate the effects of urban forest patchs on gene flow of Quercus chenii,such as the direction and intensity of gene flow.It is assumed that all seedlings within 5 m of the adult tree sample are their offspring,and other adult trees are their candidate male parents(pollen sources).The results of parental authority identification showed that only 13 seedlings(9%)found their male parents.including two seedlings(15%)in Moshan,which male parent of the seedling exists in the patch of the mother tree,and the others come from surrounding plaques.This result reflects the existence of pollen flow among individuals of Quercus chenii.In addition,due to the small number of primers in this experiment,the existence of invalid alleles may be the main reason for the low matching rate of parents.Through analyzing the forest patches in 50 m × 50 m fixed plots in four forest patches.the quantitative dynamics and diameter structure of Quercus chenii individuals in 2015 and 2020 were compared and analyzed,Results show that the age structure of Quercus chenii population was bell-shaped,with a low increase rate and a high mortality rate in five years.the death of individuals is mainly concentrated in the young stage with DBH<15 cm.We speculated that the low mortality rate of the population might be due to inbreeding decline caused by isolation caused by patchinization,in order to explore the real cause of the low mortality rate of the population.In this study,macroscopic and microscopic methods were used to reveal the influence of habitat fragmentation on Quercus chenii population in different forest patches in Wuhan,the results will help to fully understand the survivability,adaptive potential and population development trend of Quercus chenii in urban forest.It provides a theoretical basis for urban forest management and protection strategies.