Genetic Variation and Spread of Spartina alternifora in the Yellow River Delta

Spartina alternifora has been introduced into the Yellow River Delta since 1990.It spreads very rapidly and threatens the safety of the ecosystem.Investigating the genetic variation of Spartina alternifora can help understanding the mechanism of invasion and provide basic knowledge for the management of this invasive species.The genetic structure and diversity of four populations of Spartina alternifora(Pop 1,Pop 2,Pop 3 and Pop 4) at 13 loci were analyzed using microsatellite markers.The results revealed that the genetic diversity of Spartina alternifora in the Yellow River Delta was high.The average observed allele number(Na) was 7.385,the effective allele number(Ne) was 3.636,the Nei's genetic diversity was(0.700±0.094),the Shannon index was(1.453±0.343),and the proportion of polymorphic loci(P) was 100%.The Na,Ne,Nei's genetic diversity and Shannon index of Pop1 was the lowest,while those of Pop2-Pop4 were similar.However,the genetic differentiation(F_(st)=0.121) and the gene flow(Nm=1.825) among populations were medium.The genetic similarity among Pop 1-Pop 3 was high while the genetic similarity between Pop 4 and Pop 1-Pop 3 was low.As we known,Pop 3 was the initial and unique introduced population.The genetic structure of 4 populations suggested that firstly Pop 3 dispersed to Pop 4,and then Pop 3 dispersed to Pop 1 and Pop 2.The population dispersal order was not associated with the geographic distance of these populations,for the reason that the seeds of Spartina alternifora could disperse by sea water over a long distance.Therefore,developing environment-friendly herbicide to make Spartina alternifora in fecund could be a good way to control its invasion