Analysis The Genetic Diversity Of Invasive Plants Of Solidago Canadensis Based On Molecular Markers

Solidago canadensis L. is a perennial invasive alien plant belonging to Solidago L. Asteraceae, also known as the North American Solidago. In 1930s, it was initially introduced as an ornamental plant to Shanghai and Nanjing. Then it escaped into the wild and has been spreading rapidly in China in1980s, becoming one of the detrimental weeds. Because of its serious damage to ecosystem and economy development, it has already received more public attention. However, the doubts address to whether the occurred S. canadensis is only one species and what kind of biological characteristics are more likely to become invasive species. This seriously complicates the proper management of the weed. Generally, invasive plants have rapid evolution characteristics and mechanism of adaptive evolution. And the degree of genetic variation determines adaptive capacity of plant species. Therefore, from the perspective of molecular ecology it is of impotant to analyze the genetic diversity of S. canadensis of different cytotypes in order to elucidate its adaptation mechanisms and potential distribution range. This work could provide theoretical basis for the comprehensive prevention and control work.In order to clarify the successful invasion mechanisms of the invasive S. canadensis of the various regions, and the taxonomic status with its closely related species, AFLP molecular marker and ITS homologous sequences were employed to analyze the genetic diversity of S. canadensis of different ploidy, and study the correlation between genetic diversity and geographic distance and the phylogenetic relationship and the taxonomic status of the origin and invasive S. canadensis with its related species. Main objectives are to provide evidence for the identification of genus Solidago species, and a theoretical basis for clarifying the mechanism of invasion of Solidago canadensis. The main results are given as follows:AFLP technology revealed the genetic diversity of S. canadensis populations and the relationship between the ploidyThis study adopts higher sensitivity, better repeatability, abundant polymorphism of AFLP technology to analysis the genetic diversity of a total 1005 strains of different ploidy of S. canadensis, and 39 invasive populations from China, Japan and Russia,79 native populations from North America..The results showed that the percentage of polymorphic loci (PPB), the number of alleles per locus (Na), the effective number of alleles per locus (Ne), Nei’s gene diversity and Shannon’s information index of invasive range were lower than the corresponding ploidy groups from native range. It indicating that S.canadensis experienced bottlenecks in the early invasion. Regardless of origin also is invasive, genetic diversity of tetraploid populations and hexaploid populations were higher than the diploid populations, suggesting that polyploidy species has higher genetic diversity. From the perspective of genetics, it also explain that polyploidy of S.canadensis has a higher potential for invasion.After correlation analysis we found that genetic distance and geographic distance has correlation (r=0.337, P=0.01). The genetic variation present within the populations(Gst=0.2229), genetic variation depends a certain extent to the degree of evolution and reflects the characteristics of rapid evolution and mechanism of adaptive evolution of invasive species. Similarity coefficient analysis indicated that there is certain degree of genetic differentiation between tetraploid and hexaploid populations in China and different ploidy populations in north America, and the genetic consistency of hexaploid groups in Japan and the different ploidy groups from native range was higher (0.9500-0.9556), suggesting that the invasion of S. canadensis in Japan may result from the sampling area. UPGMA (unweighted pair group method analysis) cluster analysis showed that the same ploidy populations did not get together and different ploidy groups of S.canadensis may be diverse origins, The results of canonical correspondence analysis showed that, regardless of native range or invasive range, different ploidy of genetic differentiation among populations is very obvious. This differentiation resulted from pre-adaptation of Solidago canadensis as invasive plant. But the same ploidy of the native and the introduced populations genetically evolved along the longitude and the temperature habitat. The same ploidy of the native S.canadensis had space nearest, with the most similar ecological requirements. The genome doubling of the native and the invasive populations enhanced heat resistance, resulting in polyploidy of S. canadensis with new eco-environment, which was different from diploid. This is the consequnce of joint effect of the pre-adaptation in the pre-invasion and quickly adaptive evolution in the post-invasion of Solidago canadensis.The ITS sequence analysis revealed the genetic diversity of invasive S. canadensis populations and classification and relationship withits related speciesGenetic diversity of ITS sequences of a total of 79 invasive populations from China, Japan and Russia,74 native populations from North America and 12 related species or varieties of S. canadensis were analyzed and their similarity was compared through the BLAST database of the NCBI.Invasive populations of S. canadensis had lower genetic diversity than the native populations. Compared with the native American populations, haplotype diversity and nucleotide diversity index of invasive populations were lower (h= 0.108 and π= 0.00017). Low diversity indicated that invasive alien species had been subjected to the genetic bottlenecks and founder effects, probably as a result of a single or only few introductions. Homology comparison in 12 related species and varieties showed that in the invaded range, 58 Chinese,7 Japanese and one Russian invasive populations shared the same ITS sequence with S. canadensis. The similarity of other three Chinese (Changsha, Jiujiang, Shangrao) and one Russian populations (identified as S. canadensis var. hargeri Fern, based on morphological characteristics) is about 99.8%. In 10 "Huang-ying-hua" populations, ITS sequence of three populations was exactly the same as that of the invasive populations mentioned before. Although the other seven populations were slightly different, their similarity with the S. canadensis reached 99.5%-99.8%. The invasive populations were identified as S. canadensis in consideration of the high similarity with S. canadensis (accession number in GenBank:HQ142591.1). It was also found that disputed S. altissima species shared the same ITS sequences with the tested S. canadensis, and S. canadensis var. scabra Torr. & Gray (accession number in GenBank:HQ 142590.1). Moreover, their morphological characteristics cannot be clearly distinguished morphologically. Altogether,these results support Croat (1972) to merge S. altissima L. and S. canadensis L. into a single species.