| In order to understand the differences of defense strategy of plants at different successional stages upon herbivores, we compared the volatiles release of five Ficus species which are in different successional stages, i.e., typical tropical forest species/climax species: F. altissima Bl.; typical secondary forest species/pioneer species: F. hispida Linn.; intermediate species: F. auriculata Lour., F. racemosa Linn. and F. oligodon Miq. The above species were fed by a generalist herbivore Asota caricae Boisduval. as well as treated by artificial damage, and the differences of volatile releases were thereafter investigated. The major results are as follows:1. Under artificial cultivating condition, Asota caricae prefer F. hispida to F. racemosa, F. auriculata and F. oligodon, and F. altissima got the least preference when fed with a mixed leaf sample composed of the five Ficus species.2. For the leaves without damage, F. hispida released the highest amount of volatiles per cm2, which was 1190.2 pg/h/cm2. The volatiles composition included (Z)-3-Hexenyl Acetate, (E)-β-Ocimene, 1,1-Dimethyl-3- methylene- 2-vinyl cyclohexane. Next to that was F. oligodon, which was 321.3 pg/h/cm2, the volatiles included,(E)-β-Ocimene, 1,1-Dimethyl-3- methylene- 2-vinyl cyclohexane andα-Farnesene. F. auriculata released a amount of 55.0 pg/h/cm2, and the chemicals released included (E)-β-Ocimene, 1,1-Dimethyl-3- methylene- 2-vinyl cyclohexane andα-Farnesene. Next to that was F. racemosa (45.6 pg/h/cm2) and the volatitles included(Z)-3-Hexenyl Acetate, (E)-β-Ocimene and 1,1-Dimethyl-3- methylene- 2-vinyl cyclohexane. F. altissima recorded the least amount of volatile release, which was 10.2 pg/h/cm2 and the volatiles includedβ-terpinene andβ-Cubebene.3. After treated with artificial damage,all five Ficus species release more volatiles,and the net increase of volatile was similar to that leaves without damage. i.e., F. hispida got the highest amount of net increase, which was 846.6 pg/h/cm2, followed by F. oligodon 356.5 pg/h/cm2, F. racemosa 81.6 pg/h/cm2 and F. auriculata 481.6 pg/h/cm2. F. altissima got the least amount, which was 38.9 pg/h/cm2. 4. While treated with Asota caricae, the amount of volatile release changed greatly. F. hispida, got a reduced volatile release by 139.9 pg/h/cm2. Inhibited volatiles mainly included 1,1-Dimethyl-3- methylene- 2-vinyl cyclohexane. F. oligodon and F. racemosa recorded increased amount of volatile release by 220.3 pg/h/cm2 and 100.1 pg/h/cm2 respectively. F. auriculata got a significant increase of volatile release that was 2117.8 pg/h/cm2.The increased release of chemicals included (E)-β-Ocimene andα-Farnesene. The volatiles of methyl salicylate from F. hispida, F. racemosa and the jasmine pathway in F. hispida were therefore inhibted by the herbivores. The increased amount of volatile in F. auriculata and F. oligodon included some pesticide-alike chemicals suggested that this two species probably held induced defenses by volatile to insects. The data set of F. altissima was absent because Asota caricae refuse to feed it.5. Comparing the treatment of herbivore by Asota caricae to artificial damage, the number of chemical compounds was not significantly changed for the Ficus species while the amount of total volatile release and the amount of some chemicals did change significantly and different species showed different patterns.6. In conclusion, pioneer species F. hispida may use volatile'escape strategy'while climax species F. altissima adapt'constitutive defense'. The intermediate species especially F. auriculata may hold an induced volatile defense strategy twards herbivores.
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