Reproductive Traits And Adaptive Strategies Of Invasive Plant Species Coreopsis Lanceolata

Biological invasion as a global issue has received widespread attention. Clarifying the reasons and mechanisms for biological invasion is necessary to control and alleviate its damage effectively. Thus many scientists are paying great attention to exploit the traits that will bring about the phenomenon of invasion. Propagation is fundamental to form a group for the invaders. The traits concerning reproduction will exert influences on invasion. Those traits are of vital importance for explaining and anticipating the plant invasion. Therefore, the investigation of the traits in invasive reproductive biology is considered as a major field in invasive biology research.Corepsis lanceolata, one of the main invasive species in China. belongs to Dieoytledoneae, Compositae and Coreopsis. This species originates from North America and was introduced to Lu shan, Jiangxi province, China as an ornamental plant in 1936. It has spread to many other areas of China as a invasive plants and affected adversely local biodiversity. In this paper, we focus on sexual, clonal reproduction and ecophysiological characteristics of adaptation of Corepsis lanceolata in different environments, then determines the traits associated with invasiveness as well as the relationship between them. And this dissertation also attaches due attention to the ecological adaptation of its guerrilla ramets and the effect of its clonal growth on mating system, in order to discover the mechanism of sexual reproduction. I don't understand what means? The main results are as following:1. C. lanceolata normally begins to bloom in April, full totally bloom and mature from May to November. The florescence of a single capitulum lasts for about 5 to 7 days, which blooms 1-2 rounds every day. All tubular will bloom in 4-6 d. From the sixth or the seventh day, the outer-ring florets wither first, meanwhile ovary starts to develop and elongate. It lasts 8-9 d from blooming to shedding, while it takes 18 dfor fruit maturation. It takes 4-6 d from bloom to the end of pollen scatter for single tubular flowers. At the same time, and roecium mature before pistil, with anther combined to anther tube, and anther cell split inward, and mature microspore scatter enters the anther tube. With elongation of style, the gout of microspore grows higher than the anadem, then the chapiter branches into two parts and flat for pollination. Single capitulum showed that there was no seed set in single capitulum and geitonogamous, and the P/O ratio is 103549.40±7162.44, indicating that the mating system of C. lanceolata is self-incompatible. At the beginning of flowerage (for 1-4 d), the activity of pollens keeps at the rate of 94%-95%. In this process, main pollination insects are native bees, who usually visit flower before 11:30 a.m. During this period, on average 10 insects visit one florescence each 30 min. The average distance that native bees fly is 12.71 cm, and the farthest distance is 60 cm in population. They usually stay on one florescence for 10 sec. It could visit 2.59 genets between its come-and-go in population. Our results showed that high pollen viability and pollinator movement and a lot of visiting bees ensure high out-crossing rate (the yield of seeds is about 12000 per genet). Under natural conditions, the rate of germination is approximately 50%-70%, and seeds could germinate within 2-3 d under suitable conditions. The depth that the seeds are sowed affects germination significantly. Seeds germinate quickly when on the soil surface, where as the germination of seeds will be inhibited significantly when they are localized at the soil surface of 2 cm. The fertile and rich soil facilitates seed germination, suggesting that the suitableenvironment with rice resources will promote C. lanceolata invasion.2. Escaped C. lanceolata could regenerate on their own in the wild field, and spread to forest system step by step in Lu Shan of Jiang xi province. Nowadays C. lanceolata are found mainly in disturbed environment, such as along the roadside, deserted farmland and so on. These plants that co-exist with them are mostly wild grass with high adaptability. The characteristics of habitat community of different elevation indicate C. lanceolata is a kind of plant of high adaptability. The investigation, made on the characteristics of population density, environment and community of C. lanceolata in different areas of Lu Shan, shows that whatever infertile environment (such as rocky environment) or resource-rich environment (such as dessert farmland), clonal artitecture of C. lanceolata mainly consists of phalanx ramets. Because of its colnal growth and high survivality, C. lanceolata spread rapidly and dominate various indigenous plants in the area of Lu shan.3. During the whole growth season, more buds will be appeared if buds are removed, and more than 10 times of buds were produced compared with the number of buds at the end of growth season. This result shows C. lanceolata takes compensatory strategy for floral organ, and seed reproduction is a very important reproductive strategy to this species. There are many phalanx ramets originating from root during the whole growing season. The guerrilla ramets only grow in the last ten days of August. Whether the branches could regenerate ramets from stems or not has nothing to do with its contact with the soil. The branches at various developmental age have different differential ability. The aging branches'regenerating ability exceed those at the young or mature age significantly. Therefore the inhabitation via machine should be put into operation in its early stage of its growing season, and the removed branches should be dealt with properly in autumn and winter for fear that it should spread again. With the decreasing of N nutrition and light condition, the number of guerrilla ramets do not increase, i.e., the differentiation of guerrilla ramets of C. lanceolata is relevant to its life history in stead of the environment conditions. So we conclude that C. lanceolata makes best use of the resources, which is of vital revolutionary significance. Sexual reproduction could produce new genotype and seeds could be spread to new far environment. The clonal reproduction traits could help those new genotype ecesis and establish population. These results suggest that the invasiveness of C. lanceolata is closely related to its reproductive traits.4. A total of 55 individual samples selected from Virescence belt (VB) and abandoned field (AF) located in Lu Shan of Jiangxi province were studied. Eight 8 AFLP primer pairs from C. lanceolata were used to estimate genetic diversity of the population. A total of 674 bands were amplified by 8 AFLP primers, among613 of which are polymorphic bands, accounting for 90.9%. The results indicated relatively high genetic diversity of the population with the mean value of heterozygosis (h) and Shannon diversity index (Ⅰ), in which genetic diversity of AF is the highest within the patch, its Shannon informative index (Ⅰ) and Nei's gene index (h) are 0.49 and 1.57 respectively. The average proportion of distinguishable genotypes (G/N) was 0.67 in these two patches. In this paper, we simulated the attribution of different genetic ramets of C. lanceolata, results showed that different genetic ramets mixing standard influence the seed-setting remarkably. High genetic diversity of population, the pollinator movement and the guerrilla growth strategy could disperse the ramets, these traits lower the rate of geitonogamy. Therefore, the disadvantage of clonal outbreeding mating system could be avoided effectively, C. lanceolata could keep a high outcrossing rate. 5. Light condition is benefit to growth of C. lanceolata C. lanceolata is a species which favors light, and the high growth rate (RGR) and photosynthetic capacity on a mass basis (Am) contributed to improve its competitiveness under strong light environment. Under shady conditions, a significant decrease in RGR and Am of C. lanceolata reduced its competitiveness. However, other traits related to biomass allocation and resource capture-related traits, including leaf area ratio (LAR), stem mass ratio (SMR), leaf mass ratio (LMR) and specific leaf area (SLA) are not always higher for C. lanceolata than these co-occurring species even under high light condition. The reaction of C. lanceolata to light shows a master-of-some-trades pattern, indicating that C. lanceolata can only increase population densities under favorable conditions.