杓兰亚科繁殖系统转变介导的花信号趋同进化的机制

Lady's slipper orchids, subfamily Cypripedioideae, include nearly 200 species. The highly-specialized flowers with a slipper-like labellum, which supply no reward to their pollinators, make a wonderful impression for the evolutionary biologists. The Cypripedioideae deploys two types of deceptive reproductive strategies: food deception and brood-site deception. The flowers of former with bright colour displays attract bees or bees and flies for pollination, whereas the flowers of latter with dull colour exploit egg-laying flies for successful pollen transfer. Previous comparative phylogenetic evidence revealed that the transitions from bee to fly pollination independently occurred seven times in subfamily. The transitions drove the shifs from food deception to brood-site deception and also sped up the species diversification. Using reproductive ecology, biochemistry and metabolism, comparative phylogenetics and comparative transcriptomics methods, our main goal is to test whether the transitions from bee to fly pollination droven the convergent evolution of floral signals (colour and scent), and investigate how the structure of biochemical and genetic factors shape the trajectory of floral signals convergence driven by pollinator shifts. Our study will clarify the mode and their basis for floral traits evolution in Cypripedioideae, and strongly increases our knowledge on the mechanisms of floral diversification by pollinator-mediated selection.

杓兰亚科包括约200种，其花部特征高度特化，不为传粉者提供任何报酬。本亚科主要包括两类繁殖策略--食源性欺骗和产卵地欺骗。前者吸引蜂类或蜂和蝇类传粉，花色鲜艳明亮；后者只吸引蝇类传粉，花色沉暗。比较系统学证据表明繁殖系统由蜂类向蝇类传粉的转变在杓兰亚科中重复独立发生了七次，并介导了食源性向产卵地欺骗的趋同转变。然而这种转变是否介导了花信号(颜色和气味)的趋同适应和进化？其内在生化和分子机制是否也具有类似的趋同模式？本研究的目的就是利用繁殖生态学、代谢组学、比较系统学及转录组学等手段量化两类繁殖策略的花信号在表型、生化代谢、及基因表达和代谢通路上的差异，鉴定决定蝇类传粉(产卵地欺骗)花信号的相关基因网络，从而探索杓兰亚科繁殖系统由蜂类向蝇类传粉转变介导的花信号趋同进化的内在机制。本研究将会为揭示杓兰亚科花部性状进化的模式和机理奠定基础，同时为传粉者介导的花适应性进化研究提供思路。

杓兰亚科包括约200种，其传粉者主要有蜂类和蝇类两大类。处于系统发育较早分化的类群多为蜂类或蜂蝇共同传粉，而后分化的类群基本都为蝇类传粉。蜂类传粉的种类主要行使食源性欺骗的传粉策略，而蝇类传粉的种类中既有行使食源性欺骗的也有产卵地欺骗的。利用比较系统发育方法发现杓兰亚科经历了7次重复独立的由蜂类向蝇类传粉的转变，介导了食源性向产卵地欺骗的7次独立转变并促进花部UV信号的趋同进化。此外选取杓兰亚科三个独立分支（杓兰属、兜兰属、南美兜兰属）中蜂类传粉转变到蝇类传粉的种对组合，通过花色素和表面挥发物的代谢组及花的比较转录组分析，验证出杓兰亚科花信号表型趋同在转录本层面上也具有类似的基因表达或代谢通路趋同的假说，鉴定出蜂类和蝇类传粉的花UV反射上的差异可能是由于编码和调控脂（酯）类及其衍生物合成、烷烃合成、烯烃合成等蜡质合成和代谢相关的基因在两类传粉系统的花中差异表达导致的。确定了从蜂类向蝇类传粉转变过程中花信号差异的生化和分子基础。研究结果将会为揭示传粉者介导的花进化及欺骗性繁殖系统进化转变的机制具有重要科学意义。项目资助发表核心论文1篇，SCI论文1篇，待发表论文2篇。培养硕士生3名。项目投入经费24万元，支出20.8037万元，各项支出基本与预算相符。剩余经费3.1963万元，经费使用86.68%，剩余经费计划用于本项目研究后续支出。