| Ficus racemosa is a dominant and competitive tree species in tropical areas.Ceratosolen fusciceps is its obligated pollinating fig wasp.The fig wasps lay eggs by relying on the female flowers with short stigmas inside the figs of F.racemosa,so as to achieve the purpose of population survival and reproduction.At the same time,the fig wasps will also complete the sexual reproduction of figs through pollination.The complex cooperative relationship between the two species is linked by the release of organic compounds from the figs of F.racemosa.According to the current study,it was found that both the population of fig wasps and the volatiles of figs had obvious seasonal dynamics.In this paper,we analyzed the combined seasonal difference of fig wasp community and the figs volatiles to study how the fig volatiles formed fig-fig wasp specificity based on the experimental data conducted at Xishuangbanna Tropical Botanical Garden(XTBG).The role of chemical ecology in the maintenance of fig-fig wasp symbiotic network is discussed in detail.The research of this paper mainly focuses on the following three aspects:1.Community differences of fig wasps in dry and rainy seasons in Xishuangbanna.(1)There were 6 species of fig wasps in both seasons,including Ceratosolen fusciceps and five species of non-pollinators Sycophaga testacea,S.fusca,S.agraensis,Apocrypta sp.2 and A.westwoodi.C.fusciceps were the dominant species in rainy season,with an average of 458 in rainy season and 217 in dry season.The number of galls was less in rainy season than in dry season.The parasitic wasp A.Westwoodi was more abundant in the dry season,while the other two species had the opposite trend.(2)There was a significant difference in the number of fig wasps between the two seasons.The proportions of C.fusciceps in rainy season and dry season were68.53% and 45.16%,respectively,indicating that C.fusciceps were more dominant in rainy season.Besides,by calculating the species richness index,it was found that the species richness and species evenness of fig wasps were higher in the dry season.(3)In this paper,non-metric multidimensional scale analysis(NMDS)was used to calculate the stress value less than 0.2 in two seasons.The scatter plot of NMDS showed that there were certain differences in fig wasp colonies in two seasons,and the statistic R value given by ANOSIM analysis was greater than 0,indicating that the difference between species was greater than the difference within species.At the same time,Brown-Mood median was used to test the differences among the wasps.Only S.fusca,the gall maker,and Apocrypta sp.2.,the parasitoid,had no significant quantity variance,and the other four species showed seasonal quantity variance.(4)The co-occurrence network of fig wasps in different seasons was constructed in this paper.The co-occurrence network diagram in dry season was more complex than that in rainy season.In dry season,the number of sides and connections was larger,while the diameter and average path length were lower than those in rainy season,indicating that the interaction between fig wasps was stronger in dry season,and the interaction between Ficus plants-fig wasp mutualism was more disturbed.At the same time,a quantitative binary network diagram of fig wasps was established in this paper,and the nesting coefficients were 0.946 in rainy season and9.291 in dry season,respectively.The nesting of fig wasps in the two seasons was greater than the randomness.In dry season,the nesting coefficient of Ficus plants-fig wasp network was higher,indicating that the community was under strong disturbance.2.The difference of volatiles of syconium of F.racemose in dry and rainy season.(1)A total of 57 different compounds were detected in fig fruits in two seasons.The volatiles in rainy season were more than those in dry season,53 in rainy season and 21 in dry season.In rainy season,the relative proportions of each component were evener than dry season.It is worth mentioning that the highest component was benzyl alcohol which accounted for 30.92% and monoterpenes accounted for 20.14%in the rainy season.However,in dry season,there were fewer species of substances,but the content of(Z)-?-ocimene reached 70.39%.(2)There were more compounds in rainy season than in dry season.Five compounds were detected in rainy season and only four compounds were detected in dry season from F.racemosa,lacking nitrogen compounds.The volatiles produced by the F.racemosa syconium in the rainy season have a higher variability for the most component.The species and composition of volatiles of F.racemose syconium in dry season were relatively simple.(3)NMDS was used to analyze the difference of syconium of F.racemose in two seasons,the stress value was 0.The scatter diagram generated by this method could well show the difference of volatiles in two seasons.At the same time,the ANOSIM test statistic R=1,which indicated that the volatiles from F.racemosa released by the two seasons were different.3.Effects of volatiles of Ficus racemose on seasonal dynamics of Ficus plants-fig wasps co-occurrence network.(1)Based on the analysis of the seasonal differences of fig wasp colonies and volatiles,this paper estimated that the F.racemose relies on the specificity which was formed by the proportion of particular volatiles,so as to attract fig wasps.(2)The relative content of terpenoids ocimene in dry season was significantly higher than that in rainy season.From the contrastive study of differences,it was found that the syconium of F.racemose released more ocimene in rainy season to attract fig wasps into the receptive stage of syconium,or ocimene had the function of avoiding non-pollinators.To test this hypothesis,further experiments on insect behavior are needed. |
PDF Full Text Request