Research On Genetic Ecology And Sulfur-adapted Of Spartina Alterniflora

Since three ecotypes of Spartina alterniflora(F-,G-and N-)were introduced to China by Professor Zhong Chongxin,national researchers began to study morphologic characters,variations,ecotypes,invasive mechanism,ecological effects,ecological control,etc of S.alterniflora.In our research,we want to answer following questions:are there any ecotype hybrids and mixtures of S.alterniflora in coastal China;what is the genetic diversity within and among populations,and what is the genetic structure of S.alterniflora in coastal China;and if sulfur plays an important role in invasive processes of S.alterniflora.The results indicated that:Three ecotypes of S.alterniflora((i.e.Florida(F-),Georgia(G-)and North Carolina(N-))were introduced to China in 1979.Ecotype hybrid of S.alternilfora exists in the coastal China,and all four hybrids(i.e.FG-,FN-,GN-and FGN-)were examined in the coastal China,but not in every population.The first ecotype hybrid of S.alterniflora in China might be formed in a nursery plantation in Fujian.Ecotype mixture of S.alternilfora also exists in the coastal China.Such coexistence of the varieties of the species enhances the species'capacity to utilize various habitats,including open tidal flat,brackish swamps dominated by Scirpus and Phragmites species,and mangrove and uplands across a large latitudinal range from 21.6°N to 38.4°N.The mixing of various ecotypes,genotypes,and their hybrids of the species,and the continuing human disturbances along the coast of China contribute to the successful invasion and rapid spread of the species despite its overall low genetic diversity.It is highly likely that further creation of open space or suitable niche in coastal China will increase the massive expansion of the species in the future.Our genetic study suggests that,to effectively control this invasive species,greater effort should be made to control the most reproductively aggressive Florida ecotype in subtropical zones and the most competitive Georgia ecotypes in warm temperate zones,and to simultaneously reduce human activities in these regions as much as possible.Genetic diversity of S.alterniflora in the coastal China detected by AFLP markers in 2008 was lower than that reported by Travis et al.(2002),Richards et al.(2004)and Travis et al.(2005)for native populations.But genetic diversity detected by SSR markers in 2014 was much higher than that of populations.This may be due to the distances between samples in two researches are different.In the former,distance between samples we collected was about 20m,yet,in the latter,distance between samples we collected was about 40m to avoid collecting from the same clone.So far,we failed to detect any significant relationship between genetic differentiation and geographic distance among the exotic population in China by both AFLP and SSR markers.The result showed that the genetic distance between the populations of Guangxi and Zhejiang was closest,while genetic distance between Guangxi and Guangdong was farthest.We found that sulphur played an important role in invasive process of S.alterniflora.A series of our experiments found S.alterniflora actively accumulated and stored sulfur in their tissue,returned to soil or sediment through enzymely decomposition after tissue death and leaded to a high sulfide concentration in environment,by which mechanism the species successfully invaded the new habitats through increasing their competitive ability over the native dominant,Phragmites australis.Since seawater contains vast sulfate,activities of S.alterniflora that concentrate sulfur could have a substantial influence on this plant invasions.