Clonal Diversity Of Phragmites Australis And Its Effects On Ecosystem Functions In Chongming Dongtan

Global climate change and anthropogenic disturbances are altering the composition of biological communities,and impairing ecosystem functions.Recently,the relationship between biodiversity and ecosystem functions has been concerned and studied extensively,and it was proved that the loss of biodiversity has reduced the efficiency in the use of resource and energy,and also affected the stability of the ecosystem.However,most of the studies concentrated on species-diversity ecological functioning in the past,ignoring the intraspecific variation.Actually,the individual variation of the dominant species or key species which was determined by genetic diversity,also can influence the ecosystem processes seriously.Furthermore,the relationship between species diversity and genetic diversity is not always parallel,sometimes the genetic diversity is more important.In this paper,we studied the genetic diversity and fine-scale spatial genetic structure of Phragmites australis,which is one of the local dominant species in the Chongming Dongtan wetland,and conducted one manipulated experiment to test whether the ecosystem functions was affected by the clonal richness of P.australis.The results and conclusions are as follows.1.Six polymorphic micro satellite loci were obtained successfully using the biotin-streptavidin capture method.The number of alleles per locus ranged from 4 to 22 with an average of 11.6 among the 87 genotyped individuals from three populations of P.australis.Allele phenotypes was 5-42,observed heterozygosity ranged from 0.208 to 1.000,and the expected heterozygosity ranged from 0.490 to 0.881.2.The genetic diversity of P.australis distributed in the high tide of Chongming Dongtan wetland was high.A total of 80 alleles were detected in 827 common reed ramets using 8 microsatellite loci.The number of alleles per locus ranged from 6 to 15 with an average of 10.The average observed and expected heterozygosity were 0.837 and 0.776,respectively.3.The clonal richness and clonal structure of P.australis was different in different sampling sites along the high tide of Chongming Dongtan from north to south.One hundred and four genets of P.australis were found in 7 plots with the size of 20 m × 20 m sampled on a regular grid in 2 m intervals.The clonal richness varied among the plots.In the most northern site A,only 4 genets were found,and the average clone size was 30.25.Forty three genets were found in the most southern site G,the average clone size was 2.97.Sites E and F,where located in the grazing region,were dominated by several big clones.The clone size was affected by both the environmental factors and disturbance.A positive relationship was found between the soil N content and average clonal size.Spatial autocorrelation analyses showed that clonality enhanced the spatial genetic structure of P.australis in the ramet-level in all the sites.In the genet-level,the autocorrelation kinship values was significant at the scale of 4 m at site G.4.The genetic differentiation between different sites was small,and FST was between 0.005 and 0.028.Principal Coordinate Analysis also showed that the genets collected from the same site were not clustered together.We also found that the same clone shared in different sites.5.Both genotype identity and genotype richness can influence the aboveground biomass and density of P.australis.Genotype identity significantly affected the aboveground biomass and density of P.australis during three years,but the effect of genotype richness was only significant in the second year.By June 2012,effects of genotypes richness on the aboveground biomass and density were not significant,but the genotypes A,C and E were significant.After two months,genotypes richness began to influence the aboveground biomass and density significantly.The transgressive-performance of aboveground biomass and density appeared in August and October 2012,respectively.In the third year,the genotype identity was more important due to competitive genotypes.The genotype identity also influenced the number of flowers,flowering rate and underground biomass,but not the genotype richness.The interactions between time and genotype identity also effected the ecosystem functions.