Multi-cycle synchronous dichogamy is expected to be a mechanism for reducing self-pollination and sexual interference. It is often found in plants with umbellate inflorescences where pollinator movement is unpredictable, but not in plants with raceme inflorescences that are pollinated by bumblebees. Plants with raceme inflorescences often acropetally open flowers, resulting in an arrangement of females at lower level and males at upper level. This is good enough to preclude geitonogamy because bees tend to move upwardly within the inflorescences. Furthermore, although the degree of segregation of sexes varies among species, their intraspecific variations within a population have rarely been examined. Here, we present a synchronous protandry in bee-pollinated Aconitum grossedentatum, which has a raceme-like inflorescence and opens flowers basipetally. To evaluate the functional significance of synchronous dichogamy in mating, we firstly observed the distribution of sex phases of open flowers. Then, we assessed the effect of each phase flower on foraging behavior by pollinators and seed-set success. The inflorescences tended to exhibit either male- or female-phase flowers at any moment early in the flowering season, but the degree of segregation of sexes declined over time within a population. The degree of the segregation did not affect bumblebee visits to flowers, but it decreased seed-set success of female-phase flowers at that time. Our results demonstrated that synchronous protandry was beneficial for pollination success in A. grossedentatum by avoiding geitonogamy. Nevertheless, we also found asynchronous protandry late in the season, suggesting that the benefits by synchronous protandry decreased over the season.

预期多周期同步双歧是减少自花授粉和性干扰的一种机制。它通常在花序伞形花序的植物中发现，而传粉媒介的运动是无法预测的，而在总状花序被大黄蜂授粉的植物中却找不到。有总状花序的植物通常会开顶花，导致雌性处于较低水平而雄性处于较高水平。这足以阻止基因配子发生，因为蜜蜂倾向于在花序内向上移动。此外，尽管性别隔离的程度在物种之间有所不同，但很少检查种群内物种内部的变异。在这里，我们在蜜蜂授粉的总乌头中出现了一个同步的protandry，有一个总状花序状的花序，开花。为了评估同步双配偶在交配中的功能意义，我们首先观察了开放花的性相分布。然后，我们评估了授粉媒介和结实成功对各相花对觅食行为的影响。在开花季节的任何时候，花序倾向于显示雄性或雌性相花，但种群中性别的分离程度随时间下降。分离的程度不影响大黄蜂对花的造访，但它当时降低了雌相花的结实成功率。我们的结果表明，同步protandry有利于A. Grossedentatum的授粉成功。通过避免geitonogamy。但是，我们在季节后期也发现了异步蛋白质，这表明同步蛋白质在整个季节中的收益有所下降。