产卵地欺骗传粉机制及传粉者的代价：以兰科杓兰亚科兜兰属植物为例

For deceptive pollination system, currently knowledge of plant-animal interatction are mostly from the plants perspective, and little from the pollinators perspective. More investigations from the pollinators perspecitve should prove a more comprehensive understanding the evolutionarily reaction between plants and their pollinators, and a deep exploiation on the evolution of deceptive pollinaiton systems. At present, pollinators would theorectically suffer signicant costs if sexual deception causes pollinators to ejaculate and waste their sperm, and if brood-site deception causes pollinators to lay the eggs and waste their offsprings. Comparing with the sexual deceptive pollination that involved complex sexual behaviour of both male and female individuals, brood-site deceptive pollination involes only ovipositing behaviour of female individual. More important, the eggs laid by female pollinators on the flower of brood-site deception plant could be clearly counted, and the cost of the pollinators could be estimated directly. In this project, three species of Paphiopedilum (Cypripedioideae, Orchidaceae) with brood-site deception pollination system are selected. Our previous studies showed that female aphidophaour hoverflies could lay one or more than one eggs on the flower of those slipper orchids. Consequently, the pollinators will pay different cost for the brood-site deceptive pollination. Under the condition that only one egg was laid on the flower, the young larva will starve to death. Then the cost of pollinator is absolutely losing its offspring. If two or more eggs were laid on the flower, young larvae may survive by cannibalizing conspecific eggs on the same flower. And the cost of pollinator only includes part of the eggs on the flower. If two or more eggs on the flower are laid by two or more visitation, then the male fitness of slipper orchids could be increased. Therefore, two or more eggs being laid on the flower makes the realtionship between the male and female fitness of slipper orchids and the cost of the pollinator become much complex. The study of this realtionship will deleive the new insights into the relationship of antagonistic coevoluiion or an arms race beween slipper orchids and their pollinators as well as the evolution and maintenance of such plant-animal interaction. The aims of this project are: 1) to exploy the attractive mechanisms of those slipper orchids to the female aphidophaour hoverflies through field observation, quantitative measuring the floral odour and colour, and insect behaviour experiments; 2) to determine the cost pattern of pollinators in the flowers with different visiting behaviours and oviposing behaivors of female aphidophaour hoverflies, and then to evaluate the effects of brood-site deceptive slipper orchids on pollinators at individual and population levels; 3) to analyse the relationship beween the number of eggs on the flower and the pollination success of the slipper orchids.

在欺骗性传粉研究中，人们通常探讨传粉者对植物的影响，很少有人考虑植物对传粉者的作用。这种不对称的研究格局，不利于全面认识植物与传粉者之间的相互作用关系，也不利于深入探讨欺骗性传粉的进化。目前，至少在性欺骗和产卵地欺骗传粉系统中植物可能对传粉者的适合度造成不同程度的影响（传粉者代价）。相对而言，在产卵地欺骗传粉系统中比较容易确定传粉者代价是否存在，更为重要的是还可以直接定量评估传粉者的代价。本项目拟以3种典型产卵地欺骗性传粉的兜兰属植物为研究对象，通过野外观察、花颜色和气味的实验分析以及人工控制性试验等综合性手段，揭示植物吸引雌性噬蚜虫食蚜蝇（传粉者）产卵和传粉的机制；确定植物对传粉者卵或幼虫的致死模式和程度以及兜兰植物繁殖成功与传粉者在花上产卵策略和数量的关系；探讨在个体和种群水平传粉者对为兜兰植物传粉付出代价的反馈机制；进而阐明兜兰属植物产卵地欺骗传粉与传粉者之间维持进化稳定状态的策略。

欺骗性植物的花部信号被认为是适应传粉者先天视觉或嗅觉对食物，性，产卵地等模型的偏好而偏向选择出的结果。相比于食源性和性欺骗的模拟式样的研究，产卵地欺骗植物花部信号的模拟式样及其适应性演化机制的研究相对较少。兜兰属植物中，基部较早分化出的蜂类传粉种类主要行使食源性欺骗，而较晚分化出的蝇类传粉种类中既有行使食源性欺骗的亦有行使产卵地欺骗的。这两型传粉模式在兜兰属中的存在及变化式样，为研究产卵地欺骗植物花部信号的模拟式样及其适应性演化机制提供了一个很好平台。本研究基于传粉者视觉和嗅觉感受模型，对包含以上两类欺骗策略的兜兰属25种兜兰花和可能的产卵地模型（被蚜虫侵染的植物体，不同发育阶段的蚜虫等）的颜色和气味信号的相似性进行量化比较分析。我们发现，对于颜色信号，产卵地欺骗的花和被蚜虫侵染的产卵地模型的颜色位点都集中分布在传粉者视觉空间的UV区（bee-UV或fly-UV区），而与非产卵地欺骗的花（散落分布在非bee-UV或fly-UV区）相分离，且其花颜色的整体饱和度和色度变异都较非产卵地欺骗的种类低。由此推测出蝇类传粉的产卵地欺骗兜兰的花颜色信号的进化可能是由适应噬蚜虫食蚜蝇寻找和选择产卵地时对蚜虫和蚜虫侵染的植物体的视觉联合信号而定向选择出来的结果。对于产卵地欺骗的花颜色信号的进化是怎样由传粉者蜂类向蝇类的转变所介导，及造成这种转变的生态和历史因素的探究，需要后续的花部信号转变和传粉模式转变的比较系统发育分析后才能得出结论。对于花气味信号，在搭建完气相色谱质谱联用（GC/MS）设备后会补充分析。对于兜兰属产卵地欺骗的颜色模拟式样及传粉者介导的进化转变机制的结果，在完成颜色信号各个属性的比较系统发育分析后会快速整理成文。