A Comparative Study On The Biological And Ecological Characteristics Of Invasive Species Solidago Canadensis L. And Native Species Solidago Decurrens Lour.

Invasive species pose a serious threat to native ecosystem and its biodiversity, and cause considerable economic loss to the regions they invade. Solidago canadensis L. (Composite), a long-lived perennial rhizomatic plant native to North America, was initially introduced as an ornamental plant to Shanghai in 1935. It then escaped into the wild and it is now spreading rapidly in China which has become one of the detrimental weeds. The former research about S. canadensis L. mainly focused on ecological characteristics, ecological adaptabilities and control measures et al. In order to investigate the mechanisms underling its successful invasion, and try to find some effective ways to control it, the paper focuses on some aspects related to the issues about the comparison of ecological and biological characteristics between S. canadensis L. and the native specie S. decurrens Lour. The results are as follows.1. The number of plant species of communities is 7 per m2 in higher density of S. candensis; 15 in lower density; 30 per m2 of S. decurrens Lour.. The population indexes of Shannon-Wiener are 0.46, 2.08 and 2.40. The species diversity of native plant communities decreases with the expanding of the population of S. canadensis L..2. S. canadensis L. can produce as many as 38494 achenes per stem in the field. The mean weight of 1000 seeds is only about 0.041g. The light achenes with attached pappus can be dispersed readily by wind. Reproduction asexually by clone growth of rhizomes is an important way to increase populations of S. canadensis. The mother shoot can produce 6.48±2.27 rhizomes and they increases 44.42±12.66 cm each year. While every mature plant of S. decurrens Lour. can reproduce 3.17±1.85 shoots, 1697 weeds, the mean weight of 1000 seeds is about 0.494g, which is as twelve times as S. canadensis L. Compared with S. decurrens Lour., the higher ability for reproduction causes it successful invasion.3. Studies showed that allelopathic effects of invasive species were one of important mechanisms of their successful invasion. We investigated the allelopathic effects of S. canadensis and the native specie S. decurrens Lour. on seed germination and seedling growth with 6 native plants which grow in the ecosystems which the S. canadensis invades. The allelopathic activities of the water leach from different parts of the plant differed significantly, and the phytotoxic activity was also dependent on the target plant species. The present study indicated that leach of the underground parts of S. canadensis L. such as from roots and rhizomes had stronger allelopathic activity to seed germination and seedling growth of native plants compared to the others. Therefore, it is suggested that allelopathy plays a role of accomplice in the invasion of this species in China.4. Chromosome numbers of invasive plant Solidago canadensis L. and native plant S. decurrens Lour. were counted. Karyotypes of two species were analysed. The results are as follows S. canadensis L. 2n=6x=54=46m+8sm (0-6SAT), belongings to the"2A"type; S. decurrens Lour. 2n=2x=18=16m + 2sm (0-2SAT), belongings to the"1A"type. Polyploid may be responsible for the inner power of invasion of S. canadensis L..5. Many studies demonstrated that invasive species usually had rapid-evolution potential. In order to learn the genetic differentiation of S. canadensis L. after it was introduced into China, we investigated the genetic structure of the goldenrod by ISSR marker. The 12 selected primers were used to amplify the 48 individuals of S. canadensis L. from three extant natural populations in China. The results showed that there was considerable genetic variation in this species; percentage of polymorphic bands (PPB) was 95.19. The average effective number of alleles per locus was 1.5224. The average gene diversity (He) was estimated to be 0.3085. The average Shannon'index (Ho) was 0.4158. The coefficient of genetic differentiation between populations (Gst) was 0.1182 and the level of gene flow (Nm) was estimated to be 3.7304. The 48 individuals of Solidago were also amplified by 12 selected primers. And its values of PPB, Ae, He, Ho, Gst and Nm were 89.6%, 1.4425, 0.2491, 0.3834, 0.1313 and 3.3094. By analyzing the genetic parameters, this study revealed a relatively high level of genetic variation in S. canadensis L. and S. decurrens Lour. and low level partitioning (between population: 98.65%, 91.48%; among populations: 1.35%, 8.52%). The high level genetic diversity leads to strong adaptability to kinds of environment,which causes S. canadensis L. successful invasion.