Correlation Between Flowering Phenomenon,Inflorescence Thermogenesis,Floral Scent Compositions Of Rhaphidophora Peepla And Visiting Behaviors Of Colocasiomvia Flies

Some Colosasiomyia flies and Araceae host plants have already existed intimate pollination mutualism in their interaction system.Plants of the subfamily Aroideae possess inflorescences of relatively complex structure(unisexual flower,inflorescence obvious zonal differentiation,with appendix).Different parts(e.g.,male part,female part,sterile part,and appendix,ect.)of the spadix of these of plants may have inconsistent heat-producing rhythm.In addition,the effect of floral scents(volatile organic compounds,VOCs)of Aroideae plants on the flower-visiting behavior of the Colosasiomyia flies has been extensively studied.So far,little is known about the effects of the simpleness of the Monsteroideae inflorescences(bisexual floret,no appendix,no zonation)on their interaction with Colocasiomyia pollinators,especially the rhythm of heat-production and composition of floral scents these plants on the flower-visiting behaviors of the flies.In this paper,the flower-visiting behaviors of Colocasiomyia flies at different stages of the flowering period of one Monsteroideae plant,Rhaphidophora peepla,was observed.At the same time,to obtain the rhythm of inflrorecence thermogenesis of this species,temperatures of different parts of its spadix,as well the ambient temperature,were recorded during the anthesis period.Moreover,the floral scent(VOCs)of R.peepla was collected by using solid phase microextraction and dynamic headspace methods.The components were then analyzed using the GC-MS method.We also investigated the distribution of Colocasiomyia eggs in the spadix of R.peepla,with the number of eggs counted,the egg-morphology observed,and their species identified via DNA sequences.Based on the results,the correlation between the flower-visiting behaviors of Colocasiomyia flies and the flowering phenology,floral scent compositions,the rhythm of inflorescence thermogenesis of the host plant is investigated.The results showed that field observation of flowering phenology of the host plant and the behaviors of Colocasiomyia flies,the observed anthesis was divided into five stages:stages ?(the day of anthesis starting)and ?(the second day of anthesis)corresponding to the female(The spathe of the flak emitting scents,flies locating,stigma with light yellow,wet,receptivity)phase,stages ?(the third days,pollen release,flies behavior of feeding,courtship and mating),?(roughly the fourth to fifth days,with extensive pollen presentation)and ?(roughly the fifth to sixth days,anther withered and fallen off)corresponding to the male(anther dehiscence)phase.The main pollinators were C.yini and C.logivalva and the former was dominant species.Similar as previously reported,exact synchrony was observed between the flower-visiting behaviors of Colocasiomyia flies and the phenology of Araceae.The thermogenesis of R.peepla inflorescence three heat productions were observed,all maximum temperature occurred about 14:00.The first and second ones occurred during the female phase(stages ? and ?),the third one occurred during the male phase(stages ?),and exhibit maximal temperature difference between inflorescences and the ambience.The thermogenesis of R.peepla inflorescence proved to be obviously rhythmical,with nearly same thermogenesis pattern(in either rhythm or temperature)detected among the distal,medial and proximal sections of the inflorescences,which is attributable to the fundamental floral traits,i.e.,bisexual floret and spatially unzonated inflorescence of the subfamily Monsteroidean.The female phase(stages ? and ?)showed rise heat of inflorescence may be the cause of the effect of light and dark cycle and hormone.R.peepla inflorescence thermogenesis of female flowers stage(stage ?),may promote the inflorescence volatile organic compounds emited and locate host plant with flower odor signal.R.peepla inflorescence thermogenesis of female flowers stage(stage ?),may accelerate the growth of the pollen tube,improve the female gamete and male gametes fertilization success rate so as to achieve the aim of improve R.peepla seed setting rate.The male phase showed a significant rise heat of Inflorescence may be associated with the release of the pollen(inflorescence cyanide resistant way that pollen was one of the stimulus).R.peepla inflorescence thermogenesis of male flowers stage,may accelerate the the growth of stamens,dehiscence of anther dehiscence,release of pollens which were attached to the courtship behavior of flies and provided the male gamete for the next pollination.Based on GC-MS method analysed of the volatile organic compounds of R.peepla inflorescence,the composition and peak area percentage of isocitronellene compounds were the largest,more than 80%,but the odor was very weak,which compounds were more difficult to perceive for human beings;the composition and peak area percentage of terpenoids compounds were second.Because of the inflorescence volatile compounds of composition and amount are closely related to the behavior of flower visiting insects.We speculated that isocitronellene compounds and terpenes compounds may be mixed in a certain proportion as odour signals to attract flies.Taking into account also the above-mentioned results,the precise phenological synchrony between the Colocasiomyia flies and their Monsteroidean host plants indicates well evolution of intimate pollination mutualism in this interaction system.