铃铛子和赛莨菪( 茄科) 的传粉机制比较研

通过野外交配系统试验和传粉昆虫观察, 以铃铛子( Anisodus luridus) 和赛莨菪( A. carniolicoides)为研究对象, 探讨了山莨菪属内自交亲和系统的进化与传粉昆虫的转变。结果表明, 铃铛子和赛莨菪均属于自交完全亲和的类群, 但两个种的自动自交能力均不强, 而且都存在传粉限制。北方黄胡蜂( Vespula rufarufa) 和石长黄胡蜂( Dolichovespula saxonica) 分别是铃铛子和赛莨菪的主要传粉昆虫, 自然状态下两种昆虫的传粉效率均比较高, 但两种昆虫访问两种植物时传递花粉的方式不同, 其中北方黄胡蜂主要促进了铃铛子的花间传粉, 而石长黄胡蜂访花引起赛莨菪同一朵花内的传粉。通过与该属的另一种植物山莨菪(A. tanguticus) 的传粉机制比较, 发现在山莨菪属的物种分化过程中, 由自交不亲和转变为自交完全亲和, 传粉昆虫也发生了转变, 证明了自交亲和系统存在于起源较晚的类群中。高山环境中频繁且不可预测的降雨可能降低了传粉昆虫的活动能力, 进而导致铃铛子和赛莨菪均存在传粉限制。

A Comparative Study on the Pollination Mechanism of Anisodus luridus and A. carniolicoides (Solanaceae)

Empirical studies comparing mating systems and pollination mechanisms in closely related species within one genus will help us to better understand the evolution of plant mating system. In the present study, we performed field experiments on Anisodus luridus and A. carniolicoides, attempting to explore the evolution of self- compatibility and pollinator shift in the genus Anisodus. Our results showed that both A. luridus and A. carniolicoides were fully self-compatible, but the seed number and fruit set of the netted flowers without emasculation were significantly lower than the intact control flowers subjected to open pollination, indicating the two species only had a weak ability of autonomous selfing. Seed production with supplemental pollen was greatly enhanced compared with natural flowers , suggesting pollen limitation in both species. Vespula rufarufa and Dolichovespula saxonica . were the most frequent pollinators of A. luridus and A. carniolicoides, respectively. While other floral visitors , including bumblebees, flies and ants, accounted for the minority of visitation in the two species. The number of pollen grains deposited on stigmas of intact flowers within one day was significantly higher thanemasculated flowers in A. carniolicoides, but not in A. luridus . Therefore, visitations of D. saxonica to A. carniolicoides was speculated to result in selfing within flower , i . e . facilitated selfing , whereas V. rufarufa could facilitate outcrossing among flowers in A. luridus . Compared with the pollination mechanism of A. tanguticus, the putatively primitive species in Anisodus, we found self- compatibility occurred in the derived species , indicating the evolutionary transition from self-incompatibility to self- compatibility and pollinator shift during the speciation in this genus. Moreover, the unpredictable and frequent rain in alpine environment might depress pollinator activity , which could be the principal reason for pollen limitation in A. luridus and A. carniolicoides.