鼠尾草属不同物种的雄蕊杠杆机制对传粉者空间变异的进化响应

Evolutionary response of staminal lever mechanism of different species in Salvia to spatial variation in pollinators

被子植物虫媒传粉植物的物种分化通常被认为是花性状响应传粉环境(传粉者)的空间变异而发生适应性分化的结果。通过对鼠尾草属(Salvia) 3个物种(共4个居群)传粉互作系统的比较, 探索了花性状对不同传粉环境的进化响应。结果表明:各居群的传粉者组成、主要传粉者类型及其大小各不相同, 杠杆状雄蕊及相关花部性状大小在不同居群间具有显著差异; 各居群均表现出腹部传粉和背部传粉2种传粉模式, 但背部传粉仍然是最有效的传粉方式; 居群间杠杆状雄蕊长度与传粉者体长表现出极显著的正相关, 然而花冠长与传粉者体长表现出负相关; 花冠口高度和柱头高度与传粉者胸厚也表现出一定的协同变异。鼠尾草属植物的杠杆状雄蕊及相关花部性状在传粉系统的进化过程中表现出高度的可塑性, 表明雄蕊杠杆传粉机制对传粉环境的变异非常敏感, 在该属植物的物种分化过程中具有关键作用。

Aims Floral diversification in animal-pollinated species was widely believed to be driven by pollinator-mediated natural selection in response to the geographical mosaic of pollinators. Our objective was to explore the evolutionary response of staminal lever mechanism in Salvia to variation in pollinator assemblage in a spatial context. Methods We employed three species （four populations） and conducted comparative studies on pollinator-flower interactions in different populations through investigating pollinator assemblage and measuring floral traits and body size of pollinators. Important findings Floral traits investigated, including corolla length, staminal lever length and other structural traits, exhibited distinct differences among populations. These corresponded with variations in composition of polli- nators and the main pollinator and its body size in each population. The two types of pollination modes in each population were ventral pollination and dorsal pollination, which was the effective one. The main pollinator＇s body length was significantly positively correlated with staminal lever length and negatively correlated with corolla length in spatial context. Both corolla entrance height and stigma height were related to variation in body thickness of the main pollinator among populations. In conclusion, the vulnerability of lever-like stamens and other relevant floral traits to the geographical mosaic of pollinators implies the key role that the staminal lever plays in pollination, and its high evolutionary plasticity might have contributed to adaptive radiation of species in Salvia.