The Study On Genetic Diversity Of The Endangered Species Rosa Rugosa Thunb. In China And Factors Influencing Genetic Diversity

Rosa rugosa Thunb.is valuable germplasm for breeding cultivated roses,which had been ranked in the secondary protected plants.R.rugosa,is one of the dominant and important shrub species in estuary dunes and shingle beaches of northern China. However,its area of distribution and the number of populations as well as the size of each have decreased rapidly in the past two decades because of degradation and loss of habitats,and the habitats of R.rugosa have been fragmented.In the study, population ecology of R.rugosa in Muping was investigated.In every patch,patch area,arbor closure,mean height and coverage of R.rugosa,number of herbaceous species was measured.Propagating characteristic of R.rugosa was investigated in natural condition.The results showed R.rugosa mainly distributed at the edge of the forest,which were inclined to sunlight but needed some shade of arbor.In R.rugosa communities, there were few of shrubs but many herbaceous species,more than 40 species.R. rugosa were usually dominant species in communities.R.rugosa produce a great deal of fruits and seeds every year,but seedlings is seldom and soil seed band is lack.In natural habitat,R.rugosa usually propagated by rhizomes.Fifty-two insects species was observed in population MP,nine of those visited flowers of R.rugosa.Xylocopa appendiculata Smith and Leptogaster sinensis Hsia wered observed most time,both of them were dispersers of pollen of R.rugosa.Correlative software was used to analyze the data to get the relation between the mean height and coverage of R.rugosa and other indexes.The results showed:the mean height of R.rugosa had remarkable correlation with the coverage of R.rugosa (r=0.4744,p=0.0108).It suggested the coverage of R.rugosa increased with the increasing of mean height of R.rugosa.The arbor closure had remarkable negative correlation with the coverage of R.rugosa(r=-0.5474,p=0.0026),but not remarkable correlation with the mean height of R.rugosa.It suggested that R.rugosa grew dispersed to get more sunlight when arbor closure increased,but the height of R. rugosa did not increase remarkably.The arbor closure had not remarkable correlation with the patch area,which suggested shading coming from arbor did not make R. rugosa spread infinitely.The mean height and coverage of R.rugosa had not remarkable correlation with the number of herbaceous species.All results showed arbor closure was important abiotic factor to influence the growth of R.rugosa,and existing of R.rugosa did not influence biodiversity of local ecosystem in current circumstance.To study the factors influencing genetic diversity of R.rugosa,the genetic diversity of R.rugosa in population MP and correlative indexes were analyzed.These results showed:the genetic diversity of R.rugosa had not remarkable correlation with the height(r=-0.0380,p=0.8479) and coverage(r=-0.1019,p=0.6060) of R.rugosa, the arbor closure(r=0.1609,p=0.4134) and the clonal diversity(r=0.3736,p=0.0502). But the sampling number had remarkable positive correlation with the genetic diversity when sampling number was not more than 14(r=0.7279,p=0.00002).The patch area had remarkable positive correlation with the genetic diversity when the patch area is small(r=0.6434,p=0.0012).When the patch area is more than 500 m², the patch area had not remarkable correlation with genetic diversity of R.rugosa, which suggested genetic diversity of R.rugosa might be low in big patch.The number of herbaceous species had remarkable correlation with genetic diversity of R.rugosa (r=0.3927,p=0.0387),which indicated herbaceous plants could improve little circumstance in patch,and it was of advantage to success of sexual propagating.The correlative analysis between spatial distance and genetic distance showed genetic distance increased remarkably with the increasing of spatial distance.It suggested there were close relation in neighboring patch,and there were obvious genetic differentiation between patches.RAPD(random amplified polymorphic DNA) markers were applied to detect the genetic diversity of four remaining large natural populations and to discuss an effective conservation strategy of the endangered species R.rugosa in China.High genetic variations were detected in R.rugosa populations of China.The mean percentage of polymorphic loci(P%) within four local populations was 57.99%,and the percentage of polymorphic loci(P%) of the total population was 75.30%;the mean Shannon's information index(H₀) was 0.2826,and the total Shannon's information index(H₀) was 0.3513.The genetic differentiation among populations (G_ST) was 0.1878,which indicated most genetic diversity occurs within populations. Population Tumenjiang(TMJ) showed the highest genetic diversity(P%=66.27%, H₀=0.3117),and contained two exclusive bands;population Changshandao(CSD) showed higher genetic diversity(P%=59.04%,H₀=0.3065).Population TMJ contained 95.33%,and population CSD contained 99.33%of loci with moderate to high frequency(p＞0.05) of the total population.These results indicated that population TMJ and CSD should be given priority for in situ conservation and regarded as seed or propagule sources for ex situ conservation.The study also suggested that R.rugosa in China had become endangered as a result of human actions rather than genetic depression of populations;thus,human interference should be absolutely forbidden in R.rugosa habitats.This study can be referenced to establish conservation strategies for other coastal endangered species accompanied with R.rugosa,such as Vitex trifolia L.var.simplicifolia Cham.,Glehnia littoralis F. Schmidt ex Miq.,Scutellaria strigillosa Hemsl..