共享传粉者的亲缘种间花特征分化的机制：以有蜜和无蜜的两种马先蒿植物为例

Flower evolution mediated by pollinator selection has been widely recognized, especially related species have diverged in floral traits under the selection roles of different pollinators. But it’s not clear how related species pollinated by similar pollinators can diverge. The floral evolution of plants is generally associated with the rewards, with a premise that pollinators can discriminate individuals with varied amount of rewards by different attractive traits (floral signals). Pedicularis species exhibit extremely high diversity in corolla types, although which is mostly pollinated by bumblebees. Pedicularis species can be divided into two types in terms of rewards: short corolla tube with nectar and long corolla tube without nectar, which corresponds to different pollinator behaviors. This project aims to study the mechanism of floral divergence in Pedicularis kansuensis with nectar and nectarless Pedicularis semitorta. The two species of annuals representing two kinds of corolla types and rewards are closely related in phylogeny, and are sympatric and overlapping in flowering time. The two plants are very suitable to study the selective and maintaining mechanism of diverse corolla tubes.

传粉者的选择作用导致了花多样性的进化已经得到普遍认可，特别在不同的传粉者的选择作用下，亲缘种间的花特征能够产生显著的分化，但是人们不清楚由相似的昆虫传粉的亲缘物种是如何分化的，传粉者如何通过植物不同的花吸引特征（信号）识别具有不同报酬的个体。马先蒿属植物通常由熊蜂传粉，但花冠类型高度分化，根据报酬类型主要分为两大类：有花蜜短管型和无花蜜长管型。本项目选择有花蜜的甘肃马先蒿（Pedicularis kansuensis）和无花蜜的半扭卷马先蒿（Pedicularis semitorta）探讨花冠类型分化的机制。因为代表两种花冠、报酬类型的甘肃马先蒿和半扭卷马先蒿在系统发生上有最近的亲缘关系，在青藏高原东部的大部分地区同域分布、花期重叠，而且是一年生植物，非常有利于开展进化生态学、生态遗传学研究探讨花冠分化的选择因子和维持机制。

本项目以同域分布、花期重叠，且在系统发育上有最近的亲缘关系的有蜜短管的甘肃马先蒿（Pedicularis kansuensis）和无蜜长管的半扭卷马先蒿（Pedicularis semitorta）为研究对象，探讨了花性状与报酬的关系及其对传粉者行为的影响，并分析了花性状与花报酬受到的选择作用及其在年际间的变化。研究发现，传粉者对两种马先蒿的访问活动均呈现双峰型，但对两种马先蒿的日活动高峰期无重叠，存在一定互补现象，这可以有效避免两种马先蒿对传粉者的竞争和花粉扩散的种间干扰。同时，熊蜂对两种马先蒿植物的花特征偏好存在差异。甘肃马先蒿采取较多花数和高花蜜量以吸引传粉者，半扭卷马先蒿采取较大花面积和高花粉量来吸引传粉者。不同的吸引策略既对传粉者以吸引，也避开二者对传粉者的竞争。这有助于减少种间花粉干扰，促进物种共存。表型选择分析表明，甘肃马先蒿花序数更多且盔高越高，和花序数越多且花越大的个体具有更高的雌性适合度。此外，甘肃马先蒿的花蜜量受到分裂选择。但是半扭卷马先蒿的花冠性状没有受到显著的表型选择作用，说明该物种特化的花结构可能主要与雄性适合度相关。