Correlation Between Floral Traits Of Chrysanthemum (Dendranthema Morifolium) And Insect Visitors

Chrysanthemum (Dendranthema morifolium) is a self-incompatible allogamous plant. Its main pollination vectors are bees and butterflies. This paper firstly focused on and evaluated the chemical ecology and pollination characteristics of chrysanthemum with small flower type in Chrysanthemum Germplasm Resource Preserving Center of China. Our aim is to investigate and evaluate species and visiting behavior of flower-visiting insects of Dendranthema morifolium during flowering period, and the effects of flower color, corolla density, corolla diameter, tubular flower diameter, plant height and essential oils on attracting insect visitors. The volatiles from eight cultivars (or materials) of chrysanthemum with small flower type were collected by steam distilltion. Behavioral responses and electroantennogram (EAG) of Apis mellifera to the volatiles and several essential oil components of Chrysanthemum with small flower type were investigated respectively. The results as follows:(1) 32 species, belonging to Hymenoptera, lepidoptera, Diptera and Hemiptera, were observed visiting flowering D. morifolium,the species of visiting insects were not same among different months, and the effects of pollination were significantly affected by morphology, behavior and motive of flower-visiting insects. Apis mellifera was the main pollinator, which has a large population, and visiting frequency of A. mellifera was 16 flowers per min. During sunny days, visiting frequency of A mellifera and Vanessa indica were significantly positive correlation with temperature (r=0.876, 0.887, respectively), while sudden dropping-temperature, cloud and rain had important influences upon the number and species of flower-visiting insects visiting flower. Results of field observation further showed that each day, the visiting frequencies to D. morifolium inflorescences were different in different periods; generally, visiting frequency during period from 11:00 to 13:00 was the highest.(2) Bees preferred yellow colors flower to others including orange yellow, red, mauve, orange and pink. The number of visiting bees was significantly correlated with corolla density (r=0.715,p<0.01),indicating that the effect of a colony was more significant than the size of a single flower head. For all tested traits of a single flower head, tubular flower diameter had the most significant influence on attracting bees (r=0.622,p<0.01),followedby corolla diameter (r=-0.502,p<0.05).Butterflies preferred red color flowers, and tubular flower diameter significantly influenced the number of pollinating butterflies (r=0.635, p<0.01).Results suggested that rewards from the flowers were the dominating attractive factors to visitors. The effect of single flower head on number of visiting butterflies was more significant than corolla density (r=0.487,p<0.05). In all tested traits of a single flower head, flower color and tubular flower diameter were the main influencing factors on numbers of visiting butterflies.(3) The main essential oil components,such as camphor (r_bees-0.191,p>0.05; r_butterflies=0.507,p>0.05) and borneol (r_bees=0.354,p>0.05;r_butterflies=-0.387,p>0.05) had little correlation with number of visiting insects, whereas some specific essential oil components, such as camphene (r=-0.909, p<0.05), 2-pentadecanone,6,10,14-trimethyl-(r=0.882,p<0.05) showed significant correlations with number of visiting bees, andα-terpineol (r=0.979, p<0.01),cis-limonene oxide (r=0.979, p<0.01),E-farnesene epoxide (r=0.979, p<0.01),p-mentha-6,8-dien-2-ol, cis-(r=0.973,p<0.01),p-menth-1-en-8-ol (r=0.962,p<0.01) and p-menth-1-en-4-ol,[R]-[-]- (r=0.957,p<0.05) showed significant correlations with number of visiting butterflies.(4) The number of visiting bees was significantly correlated with seed setting percentage (r=0.534, p<0.05) .(5) The olfactory responses of Apis mellifera to volatiles from different cultivars (or materials) were different, and the positive response became greater as the concentration decreased. Apis mellifera was significantly attracted by 0.1μL/mL^-1 'jin ling chun meng' and 'jin ling wan xia' volatiles (coefficient of selectivity are 0.72 and 0.63 ). Apis mellifera also has different responses to volatiles from different cultivars (or materials) of chrysanthemum with small flower type, the EAG values of Apis mellifera treated by volatiles of 04-1-29 and 'jin ling shuang xiu' were significant higher than the other cultivars (or materials) (p<0.05),while the values treated by volatiles of 'jin ling jin pao'and 04-8-8 were lower than the other cultivars (or materials)(p<0.05). (6) Apis mellifera has different responses to volatiles from different aromatic constituents of chrysanthemum with small flower type, the EAG values of Apis mellifera treated by bomeol acetate were significant higher than the other components (p<0.05).The olfactory responses of Apis mellifera to different components of volatiles were also different, Apis mellifera manifests obvious positive tropism to 0.01μL·mL^-1CaryophyIIene oxide (coefficient of selectivity is 0.60),while negative tropism to 1μL·mL^-1 Camphor (coefficient of selectivity is -0.65).