Molecular Taxonomy Of Sarsassum Fusiforme And Sarsassum Genus, And Population Genetics Of S. Horneri And S. Fusiforme

The mitochondrial cox1, chloroplastic rbcL, and nuclear ITS (including partialITS1,5.8S and partial ITS2) regions were used to assess the taxonomic relationshipand classification of10species of genus Sargassum and one of genus Turbinaria. Andthese33sequences and related sequences from NCBI were aligned and analyzed. Themolecular phylogenetic analysis showed that S. fusiforme could be regarded as onesection in the subgenus Bactrophycus of the genus Sargassum; in addition, othermolecular phylogenies of Sargassum species collected from China were eitherdiscussed in our study.Two molecular markers system, Inter Simple Sequence Repeats (ISSR) andSequence Related Amplified Polymorphism (SRAP), were applied to analyze thepopulation genetics of nine natural Sargassum horneri (Turner) C. Agardh and S.fusiforme (Harvey) Setchell populations of China. For ISSR and SRAP markers,respectively, percentage of polymorphic loci (P%,99.44%,100.00%), Nei's geneticdiversity (H,0.1067-0.1985,0.1003-0.1532) and Shannon's information index (I,0.1569-0.2907,0.1480-0.2188) exhibited the population genetics of S. horneri. Genedifferentiation (GST,0.6538,0.7182) implied that significant differentiation amongpopulations may be as a result of habitat fragmentation and limited gene flow (Nm,0.2648,0.1962). Both matrices of genetic distances and fixation indices (FST) amongpopulations had high correlations with geographical distribution when the RC(Rongcheng) population was removed. On the whole, genetic differentiation agreedwith Isolation by distance (IBD) model.To the S. fusiforme populations, of the255loci generated by21ISSR primers,99.61%were polymorphic and99.71%of344bands amplified by30SRAP primers were polymorphic. The tested high genetic diversities showed that the average H were0.1519and0.1624, and average I were0.2248and0.2400in ISSR and SRAPanalyses, respectively. Unweighted pair group method with arithmetic mean (UPGMA)dendrograms of the nine populations were divided into two main groups. For ISSRand SRAP analyses, values of gene differentiation (GST,0.5955,0.5486, respectively)indicated that high variation existed among the nine populations, likely due to externalinterferences and limitation of gene flow (Nm,0.3397,0.4114).