Pollinator Composition And Behavioral Ecology Of The Main Pollinators For Jatrovha Curcas L.

Jatropha curcas L. is an important biodisel shrub in Southwestern China. The kernel of itsfruit is rich in fatty oil, an excellent raw material for biodisel. At present, J. curcas has beenplanted in a large scale in Southwestern, Southern China, especially in Southwestern China.Previous studies reported a few of its pollination biology, such as floral visitors, visitingbehavior and breeding system. In order to understand the intrinsic connection between floralcharacteristics of J. curcas and pollinators and pollinators, this paper observed the pollinatorsand their pollinating behavior at four sites, studied the visual and olfactory attractiveness offloral attractiveness to main pollinators, and tested the contribution of different pollinatorgroups to the female reproductive success of J. curcas. The results are summarized asfollows:1. Geographic distribution of pollinatorsThe study was investigated at four sites. The results showed that J. curcas wasgeneralized pollinated plant, with a range between34species and45species at each sites, and113species at four sites in total. Pollinators were divided into seven functional pollinationgroups including honeybees, solitary bees, ants, Diptera, Coleoptera, Lepidoptera andHemioptera. Pollinator composition is completely similar at function pollinator group, buthighly dissimilar at family, genus and species level among four sites. Pollinators distributedwidely in zoogeographical regions in the world, as well as in China. Thus, J. curcas couldattract diversified functional groups of pollinators and were generalized pollination plant.Pollinator composition was influenced by the inhabitation of J. curcas, while pollinators oftendistrubitued broadly both in the zoogeographical regions of world and that of China.2. Main pollinators and their foraging behaviorThe paper studied the abundance of visitors, predators, the floral reward, pollen grainscarried by pollinators, body part carrying pollen grains, pollination efficiency and preferencefor flower sex, then analyzed their effect on reproductive success of J. curcas. The resultsshowed that main functional pollination groups were honeybees, ants, Diptera and Coleoptera.Predators for visitors were spiders, mantis etc.. The most important reward for floral visitorswas nectar. All major functional groups carried pollen grains with them, and quantity ofpollen grains adhered to different body parts were different. Honeybees and Diptera only carried pollen grains of J. curcas, due to their flower constancy or cleaning off of body partfrequently, which played an important role on the homoscedasticity of all pollen grainsdeposited on its stigma from that of J. curcas. Major body part of pollination was basalproboscis for honeybees and Diptera, was abdominal for beetles. The quantities deposited ondifferent stigmas of female flower after single visit of A. cerena and C. megacephala weresignificantly different. Thus, more than one visit of A. cerena and C. megacephala wouldhelp enough pollination of female flower. A. cerena and A. florea preferred to male flowers,and C. megacephala did not show preference, while the preference of former pollinators mightcause low pollination rate of J. curcas. Thus, honey bees and Diptera were capable of carringover abundant, homogenous pollen grains, transfering pollen grains efficiently throughproboscis-touch pollination. However, pollination efficiency could be decreased by bothunbalanced pollen deposition among three stigmas of honey bees and preferrence of honeybees to male flowers.3. Visual attractiveness of floral characteristics to its pollinatorsThis paper observed the micro-characteristics of pollen and stigma, flower sizes of bothmale and female flowers, tested the effect of floral component, petal size and floral color onpollinators, and observed the floral display of inflorescence under drought stress. The resultsshowed that stigma of J. curcas was dry type, but pollen grain is rich in water and large-sizedin diameter which might help adherence and germination of pollen grain. Corolla diameter offemale flowers was larger than that of males while the diameter of stamen was larger than thatof pistils. There was no significant difference between the corolla tube length of male flowersand that of females, and between the length of stamen and pistil, which might help theconverting of pollen grains. Both male and female flowers could emit fragrance, mainly frompistil and ovary might increase the attractiveness of flowers to pollinators. Removing petalsor stamen could decrease the attractiveness of flower to honey bee and Diptera, whileremoving calyx did play any role on the attractiveness. Decreasing of petal size woulddecrease the attractiveness of honeybees and Diptera. Change of stamen color woulddecrease the floral attractiveness to honey bees, but did not to Diptera. Inflorescences underdrought stress showed protandry which showed small floral display of female flowers withinan inflorescence, and, therefore, might decrease the pollination rate of female flowers. Thus,flower of J. curcas attracted honey bees and Diptera through floral composition, petal sizes andpistil colour.4. Olfactory attractiveness of floral volatile to its pollinators Floral and foliage volatiles of J. curcas were collected by head space and离体, and thendetected, analyzed and identified. EAG responses of A. cerena to floral volatile of J. curcasand to different intensity of volatile were detected. Olfactory behavior responses of A. cerenaand C. megacephala to different odour source were detected. The results showed that themost abundant chemicals from flower and leave of J. curcas were ocimene and linalool,followed by aliphatic compounds. Floral and foliage volatile emitted most linalool in themorning, and emitted a little or did not emit linalool in the afternoon and at night. Similarly,opening inflorescence released most linalool, while unopen and opened inflorescences emittedlittle linalool. All tested floral volatiles elicited EAG response of A. cerena, while linalooland all fatty aldehydes elicited high EAG response. Dose response curves of EAG showedthat A. cerena response to the bottom dose of tested volatiles ranging from0.4μg to4μg.The EAG response of A. cerena increased with increased dose, and did not reach its saturationspot at maximum tested dose. Olfactory behavior response showed that A. cerena respondedstrongly to floral volatile of J. curcas, while C. megacephala showed little response. Thus,floral volatiles of J. curcas attracted A. cerana, and did not attract C. megacephala.5. Contribution of diurnal and nocturnal visitors to the pollinationI examined the contribution of diurnal and nocturnal insects to the pollination ofmonoecious J. curcas, through its floral biology, pollination ecology of J. curcas and foragingbehavior of potential pollinators at Shuangbai. Nectar production of both male and femaleflowers peaked in the morning, declined in the afternoon, and rapidly bottomed during thenight in all of their anthesis days. The diurnal visitors to the flowers of J. curcas are bees andflies, and the nocturnal ones are moths. Flowers received significantly more visits by diurnalinsects than by nocturnal ones. Through bagging flowers during night or day or both orexclusion, we compared fruit and seed production caused by diurnal and nocturnal pollinators.Both nocturnal and diurnal visitors were successful pollinators. However, flowers exposedonly to nocturnal visitors produced less fruits than those exposed only to diurnal visitors.Thus, diurnal pollinators contribute more to seed production by J. curcas at the study site.6. Ants contributed significantly to the pollinationFloral visitor assemblage and foraging behavior of ants were observed, pollen loadscarried by ants and deposited on stigmas were measured, and the contribution of ants to thefemale reproductive success of J. curcas through exclusion experiments were determined atShuangbai and Yuanmou. Ants were the most abundant pollinators, accounting for71.03% and78.17%of total visits at two study sites. Among different ant species, Tapinomamelanocephalum is always the most abundant and the only common ant species at two studysites, which might suggest its important role in the pollination of J. curcas. Pollen loadscarried by ants were significantly different among different species at two study site. Pollenloads carried by ants increased with increased body length. Pollen loads deposited on stigmaswere significantly different in the open group, winged only, ants only I, ants only II, ants onlyIII, respectively. Although the flowers exposed only to ants produced less fruit than thoseexposed only to winged visitors, ants alone resulted in almost60%fruit set. Thus, ants couldplay a major role in the pollination of J. curcas if winged insects are absent.