Comparison Of Extrafloral Nectar Mediated Defense Between Native And Introduced Passionflower

EFN (extrafloral nectary) plant is a special group of plants. They have nectaries on the other part of the plant more than just in the flower. Those nectars seldom involved in pollination. Most EFN secretions contain sucrose, glucose, fructose, and some amino acids. These sugars attract ants, parasitoids and many predators. Ants come for extrafloral nectar may prey on or disturb herbivores, thus formed the mutualism between plant and ant. We studied the mutualism relationship between ant and plant in the natural habitat of Passiflora siamica with two EFN plants Passiflora siamica (endemic) and Passifora coccinea (introduced). The main results are as follow:1. At least 24 ant species were recorded utilizing the EFN resource. Include Paratrechina sp.1, Dolichoderus thoracicus (Smith), Tapinoma melanocephalum, Pheidole yeensis. One species from Ponerinae, one from Pseudomyrmecinae, nine from Myrmicinae, two from Dolichoderinae, eleven from Formicinae.2. No significant difference was found between the number of ants visit two species of plants (t=1.30, P=0.20), while the compositing proportions of the main four ant species were different in the two Passiflora plants (x2=14.76, df=4, P< 0.01).The quantity of nectar secreted by a single leaf of Passiflora siamica is significantly higher than that of Passiflora coccinea plants (Willcox, z=-3.87, P< 0.01).Ant-excluding in this experiment do not significantly affected the average leaf loss per plant. For each species of plant, no significant difference of leaf nectar quantity was found among treatments.3. The leaf trichome density of both side of Passiflora siamica leaf were significant lower than Passiflora coccinea, (upside leaf, t=-3.28, P< 0.01; underside leaf, t=-26.84, P< 0.01). In Passiflora siamica, the average leaf loss per plant was significant correlated to leaf trichome density of the undersider leaf (Pearson correlation, r=-0.38, P=0.04, n=30), but in Passiflora coccinea wasn't. 4. The average leaf loss (Log(x+1) transformed) of P. siamica was significantly correlated with the number of ants per plant (square root transformed) (Pearson correlation, r=-0.45, P< 0.05, n= 20). Ant behavioral dominance index (BDI, an index calculate as the proportion of dominance times to total encounter times of a species of ant to all other ants species in the same community) was significantly correlated with species total abundance on plants (Pearson correlation, r=0.86, P =0.01).As a whole, the plant-ant-generalist herbivore in the two Passiflora species did not show a significant differences in the response to the change, while the interactive system with specialist herbivore request further investigation.