Studies On Reproductive Trait And Seeding Recruitment Of Typical Clonal Plant Ligularia Virgaurea In Qinghai-Tibet Plateau

Reproduction is the critical issue to understand the evolution of plants. The pattern-of resource allocation during the reproductive stage has profound impact on the evolution of plant life history. However, the resources availability in nature is pretty limited. To realize maximize fitness, plants must allocate limited resources or energy into different functions, and must trade-off the functions between growth and reproduction, male and female. Ligularia virgaurea (Maxim.) Mattfl. is a kind of relatively evolutionary species in ligularia Cass. in Compositae and is also one of a few species of the genus distributed in the higher altitude region. Ligularia virgaurea, a typical clonal plant in alpine meadows on the eastern Qinghai-Tibet plateau, in an herbaceous perennial plant has clonal reproduction by rhizomes and sexual reproduction by seeds. Recently, the alpine meadow seriously deteriorated and L. virgaurea has become one of advantage toxic weed in eastern Tibet, because of continual over-grazing and selective predation by livestock. Therefore, we conducted observational and experimental studies to investigate how the sexual and clonal reproductions adapt the environment, including biotic and abiotic factors, and to understand the relationships between sexual and clonal reproductions. The results showed:The pattern of biomass allocation in L. virgaurea is influenced significantly by light and nutrient conditions. The expression of plasticity in clonal growth and reproduction may be influenced by the available resources. L. virgaurea puts resources to clonal reproduction at the expense of vegetative growth in mother plant. However, no trade-offs were found between sexual and clonal reproduction in L.virgaurea. The ability of seedling recruitment may be significantly influenced by environmental condition and community succession stage. Despite the dominating role of pollinators in floral evolution, our results reveal significant additional, often antagonistic, influences of abiotic and biotic non-pollinator agents. Our study also showed several patterns of variation from top to bottom capitula, including an increase in bisexual flowers and flower number per capitulum, but a decrease in seed set and size. We suggest that these variations may help to enhance reproductive success of L.virgaurea in the face of bisexual-biased seed predation. The evolution and maintains of gynomonoecious system are also discussed.