The Correlation Between Nectar Volume And Floral Characters And Its Adaptive Value In Aconitum Gymnandrum

There are many factors can cause variation in nectar production of a flower. Plants attract pollinators through several signals of floral display. Pollinators fulfil pollination process while foraging nectar. Therefore, signals of floral display must have a strong correlation with nectar volume, or it can represent "faithful signals" of nectar volume so as to maintain a stable and mutually beneficial relation of the plant-pollinators. There are many factors can cause the inter-and intra-plant variation of nectar production, To explore the influence factors of nectar volume variation, the correlation between floral characters and nectar volume influences the insect visiting frequency and the plant fitness, in this study we investigated the variation of nectar production as well as its influence factors, effects of different flowering time (between and within individuals), the correlation between the nectar volume and floral characters, the phenotypic selection of these traits in growing season, then we discussed the maintaining mechanism of mutually beneficial relation of plant-pollinators in protandrous Aconitum gymnandrum.There was significantly positive correlation between mean nectar volume per flower and flowering time of individuals, the fewer mean nectar volume per flower in earlier flowering individuals; Within individuals, flower position within inflorescences had significant effect on nectar volume per flower. Basal flowers produced more nectar than distal ones and thus lead to a declined nectar gradient along inflorescences. A. gymnandrum did not show gender-biased nectar production. But there was a significant variation of nectar volume in the process of development of flower, with the increasing percentage of anther dehiscence, nectar volume emerges non-linear increase, while the value of nectar volume reaches a maximum at the end of the female phase.Although the attractive features of floral display are likely to have evolved to advertise rewards, the results showed that attractive features such as petal width and petal length have no significant positive correlation with nectar volume, especially correlation between petal length and nectar volume was opposite in two years. There were different correlation between nectar volume and initial flowering time in two years, which suggests that environmental factors can influence the variation of nectar volume and the correlation of nectar volume with floral traits.The significant linear selection differential and gradients on floral traits were estimated respectively through female fitness which was represented by pollen number and seed number respectively were different in the different years and estimated under the different female fitness components. The individuals with greater nectar volume had higher female fitness(the number of seeds), but these interannual selections were different. Generally, earlier flowering time and higher petal length were advantageous to improve the individual female fitness, these interannual selections were stable. Nonlinear selection analysis showed that there were no significant correlation between nectar volume and floral traits. The results also showed that individuals with the earlier flowering time and the less floral number had more seeds; the individuals with higher petal length and wider petal width had more seeds. But the interannual significant nonlinear selection of flowering time were opposite.