Studies On The Phylogeography And Clonal Reproductionof Two Sparganiumspecies In Northeast China

Rivers and mountains are often considered to be important factors affecting the geographical distribution of plants.There are many mountainous and rivers in Northeast China,which affects the population genetic structure and genetic differentiation of aquatic plants in the region.We used three chloroplast DNA(cpDNA)fragments,two nuclear gene fragments and five microsatellite loci to study the phylogeography and clonal reproduction of two Spargamium species,S.angustifolium and S.glomeratum in Northeast China.The main results are as follows:The levels of genetic diversity of S.angustifolium and S.glomeratum were low.The genetic diversity in cpDNA of S.glomeratum was higher than that of S.angustifolium,whereas the genetic diversity in nuclear gene and microsatellite loci of S.angustifolium was higher than that of S.glomeratum.It was probably caused by different inheritance patternsof cpDNA and nuclear DNA and different evolutionary historis and sexual reproduction modes of these two Spargamium species.AMOVA results indicated that the major of genetic variation occurred within populationsin S.angustifolium,and in S.glomeratum,most of genetic variation occurred among populations.The level of genetic differentiation in S.glomeratum was higher than that of S.angustifolium.It was likely related to their different sexual reproduction methods and life forms.AMOVA,genetic differentiation coefficient comparison and STRUCTURE analysis showed that these two Sparganium species had no obvious phylogeographic structure in the Northeast China.The geographical distribution of their gene lineages was inconsistent with the division of river basins,indicating that the mountain among river basins was not the barrier of geneflow and geneflow existed among different river basins.The levels of clonal diversityof S.angustifolium and S.glomeratum were low,indicating that their populations had a high proportion of clonal reproduction and the proportion of sexual reproduction was low.The inbreeding coefficient of S.angustifolium was less than 0,indicating thatits main mode in sexual reproduction is outcrossing.The inbreeding coefficient of S.glomeratumwas greater than 0,indicating its main mode in sexual reproduction is selfing and inbreeding.Their different mating systems are consistent with their inflorescence characteristics.In conclusion,the levels of genetic diversity of S.angustifolium and S.glomeratum were low;the level of genetic differentiation in S.glomeratum is higher than that of S.angustifolium;the proportion of clonal reproduction is high in these two Sparganium species;outcrossing and selfing/inbreeding are the main modes of sexual reproduction in S.angustifolium and S.glomeratum,respectively;and these two Sparganium species have no obvious phylogeographic structure in the Northeast China.This study provides a reference for aquatic plant phylogeography in Northeast China,and helps us understand the evolutionary history of aquatic plants in Northeast China.