Genetic diversity, population structure, and genetic relatedness of native and non-native populations of Spartina alterniflora (Poaceae, Chloridoideae)

Spartina alterniflora Losiel. is a highly invasive species found on the Chinese coast. To characterize the evolutionary mechanisms underlying the success of S. alterniflora in China, we examined the distribution and structure of genetic variation among three native populations at their source locations and five non-native populations in China, at both the chloroplast and nuclear microsatellite loci. Both cpDNA and microsatellite data revealed comparable genetic diversity and population differentiation between the native and introduced regions, which is consistent with the deliberate historical planting of heterogeneous founding groups in China. Bayesian clustering analysis showed that the best two clusters in the introduced region correspond to populations from the Atlantic coast and Gulf coast, respectively, instead of the three ecotypes proposed by a previous study. Investigating genetic composition of individuals suggested that most of the non-native plants might be of Atlantic origin, while some individuals in the Hong Kong population could be genetic admixtures of Atlantic and Gulf origin. This study indicated varied genetic components among populations in China, which imply different sources for the present Chinese populations.