The Study On Factors Influencing Invasions And Genetic Diversity In Alien Species Coreopsis Grandiflora Hogg

Because of the influence of anthropogenic activities and global change, biological invasions of alien species have become a universal problem. Because of its significant ecological impacts and economic costs, biological invasions have attracted extensive attention from ecologists and people worldwide. Biological invasions not only were influenced by the global changes, but also are itself a part of global changes. Invasive species are believed to be second only to habitat loss in terms of their impact on native diversity. Biological invasions not only threaten native biodiversity but also cause a considerable economic loss.Coreopsis grandiflora Hogg. is a decorative plant, belongs to Compositae, which was introduced to China as a flower from America, and sexual reproduction is the main reproductive mode. About 2001, C. grandiflora was paid attention. Recent years, the study of alien species centralized on some alien species which had produced huge damage, such as Spartina anglica Hubb., Eupatorium Adenophorum Spreng. and Altemanthera philoxeroides (Mart.) Griseb., and most studied invasions happened in South of China. Most studies of genetic diversity of alien species focused on the clonal plants. Studying the alien species that have potential ability to invade a new habitat and the genetic diversity of alien species with sexual reproduction was very important for understanding the process and mechanism of biological invasions.In the study, the method of field research and sampling was adopted to set different plots in different altitudes (950m, 750m, 650m, 550m, 350m, 300m and 250m).Sseveral 1×1m samples were set in plots. In every sample, the coverage, sociability and height (average and the most maximum) of C. grandiflora, the coverage of sample, the coverage, abundance and height of the native species was measured. Correlative software was used to analyze the data to get the relation between the coverage of C. grandiflora and other indexes. The results showed: the coverage of C. grandiflora had remarkable correlation with the coverage of samples (r=0.7060, p=0.000001). It suggested that the coverage of C. grandiflora increased with the increasing of coverage of samples; the coverage of C. grandiflora had remarkable negative relation with the abundance of the native species (r=-0.5193, p=0.0010) and the native species coverage (r=-0.4311, p=0.0025). It suggested that with the increasing of the coverage of C. grandiflora, the abundance and coverage of native species decreased. In addition, with the altitudes increasing, the coverage of C. grandiflora decreased (r=-0.8926, p=0.0068). All these results indicated: the invasion of C. grandiflora had produced huge damage to the biodiversity of native species in Laoshan Mountain, even had the trend forming the single population; the distribution of C. grandiflora always along the road, and altitudes had important influence on the spread and distribution, it can reflect the spread path of C. grandiflora.After the alien species established the population, with time passing, genetic differentiation and variation may occur. The study on the genetic diversity of alien species is a new field, which can be favor of understanding the evolution of alien species, and provide the theoretic evidence for exploring the measure of controlling and elimination. RAPD was used to study the genetic diversity of C. grandiflora, and revealed the genetic variation was high in the introduced populations with sexual production which is different from other previous studies and studied the possible spread path by studying the genetic diversity of C. grandiflora.To study the genetic diversity, we sampled in Boshan and Laoshan Mountain and used CTAB to extract DNA, and got the RAPD bands pattern according to PCR and the technique of agrose gel electrophoresis. Popgene was used to analysis dates. We found: there was high genetic diversity of C. grandiflora in Laoshan Mountain, the percentage of polymorphic loci ranged from 9.60%-60.80%, there was a great difference and the mean value was 39.54%. The percentage of polymorphic loci was 86.40% among populations. Compared with C. grandiflora in Boshan, the percentage of polymorphic loci was 92.86% between populations. The average Nei's gene diversity index (H) within populations was 0.1596, and 0.2855 among populations in Laoshan Mountain. Compared with C. grandiflora in Boshan, the Nei's gene diversity index (H) was 0.2988 among populations. This suggested the genetic variation among populations in Laoshan Mountain and Boshan was bigger than in Laoshan Mountain. The genetic diversity decreased with the increasing of altitude in Laoshan Mountain. All these results suggested that genetic variation was high. Except the sexual reproduction, the multi-origin of C. grandiflora in Laoshan Mountain may bring the result that the genetic diversity of C. grandiflora in Boshan was lower than that in Laoshan Mountain. The mode of transmission of seeds of C. grandiflora in Laoshan Mountain may be from low altitudes to high altitudes.According to the study, the genetic distance (D) among populations of C. grandiflora in Laoshan Mountain was little compared to Boshan. In Laoshan Mountain, the least genetic distance consisted in pop6 and pop7 (D= 0.0664), the maximal genetic distance consisted in pop4 and pop5 (D=0.2231). Compared to Boshan, the least genetic distance consisted in pop6 and pop8 (D= 0.2362), and this genetic distance was bigger than the maximal genetic distance in Laoshan Mountain. According to dendrogram, all populations were compartmentalized to three groups, one group was made up of the populations of pop5, pop6 and pop7; another group was consisted of pop1, pop2, pop3 and pop4;Boshan population belonged to the third group. All this results suggested: the genetic relation among populations in Laoshan Mountain was near to each other and was with the Boshan population. There maybe relation between these results and the seed origion.To study the factors influencing the genetic diversity of C. grandiflora, the genetic diversity of C. grandiflora and correlative index were analyzed. These results showed: the genetic diversity of C. grandiflora hadn't remarkable relation with the coverage of C. grandiflora (r=0.0267, p=0.8632), the coverage of native species (r=-0.0610, p=0.6940) and the abundance of native species (r=-0.1094, p=0.4797). But the sampling size had remarkable positive relation with the genetic diversity (r=0.8880, p=0.0032). The dendrogram of all samples was did and found: the sample at the same altitude and consecutive altitude had near relation. This result showed again that the relation between Laoshan Mountain and Boshan was relative farther, which suggested that the geographical isolation interrupted the gene flow.The relation between genetic diversity and the invasion was studied and found there was no remarkable relation in the scale of this research. Only the influence of the population indexes of C. grandiflora on the genetic diversity was studied, but the genetic composition of an invasive species is influenced by many factors, such as the history of introduction, life-history characteristics, founder effect, gene drift, and the breeding system. To further study the relation between genetic diversity and the invasion, I suggested to carry out the research in a bigger scale in the future, and should analyze multi-factor.At present the loss produced by alien species in North of China was relatively slighter than in South of China, but their threaten was also exist, so we should take some action in time to avoid great damage. The genetic diversity of C. grandiflora with sexual reproduction was studied and found there was high genetic diversity, and most of genetic variation occurred within populations. Altitudes had great influence on the genetic diversity of C. grandiflora, the genetic diversity decreased with the increasing of altitude in Laoshan Mountain. The genetic diversity had remarkable geographic variation between Boshan and Laoshan Mountain.