Study On Non-pollinator-plant Interactions And Floral Evolution In Response To Non-pollinator’s Selection

Adaptation and evolution of floral traits has been continually concerned by evolutionary biologists. In recent years, more and more studies showed that the evolution of flowers has usually been incorporated into some conflicting selection systems, while less attention to biological factors other than pollinators such as nectar robbers and seed predators. In this thesis, we address the correlations among these factors by studying Salvia przewalskii Maxim, an endemic plant in western China. We also combined biotic and abiotic factors to investigate adaptive mechanisms on plants,trying to uncover the mystery of cupular bracts and evaluate herbivore-pollinator interactions in Pedicularis rex, an alpine plant in Hengduan Mountains Region, China.Cupular bracts were observed to be full of water, where most part of corolla tube of flowers submerged. We present our major results as follows.1. The pollinating-behaviours of bumblebees in Salvia przewalskii have been interrupted when honeybees are present, which reduced the visitation rate of legitimate bumblebees markedly.2. The robbing frequency of S. przewalskii flowers negatively correlates with the density of legitimate bumblebees; Seed setting rate at population level also negatively correlates with robbing frequency.3. The cupular bracts of Pedicularis rex(with the water therein) significantly reduced the probability of oviposition on flowers by insects, enhancing the reproductive success in rainy environments.4. Plants deemed to be large on the basis of stem diameter and leaf size tended to have large cupular bracts and long flowers but small corolla tube diameters and corolla openings.In a multiple regression that included six floral traits as predictor variables,stigmatic pollen load was highly predicted by flower length and corolla opening. The ratio of bract height to-flower length was observed to be negatively correlated with both stigmatic pollen loads and seed predation, indicating that the extent to which the long corolla tubes emerge above the water in the bracts influenced pollinator visitation and florivore oviposition.Our study on Salvia showed that introduced honeybees disturbed legitimate pollinator-plant interactions and facilitated nectar robbing that reducing plant reproductive success. Our study on Pedicularis indicated that the long corolla tubes that allow flowers to emerge further above the water may facilitate pollination but also promote high seed predation, suggesting that the same traits can be subject to conflicting selection from pollinators and florivores.