蓝翠雀花退化雄蕊上的黄色髯毛对其繁殖成功的影响

蜜导是一类对传粉者具有特殊吸引和指示作用的花图案或花结构,在被子植物尤其是虫媒花中普遍存在,但目前有关蜜导对植物繁殖成功影响的研究相对较少.在野外条件下,我们以毛茛科翠雀属的蓝翠雀花(Delphinium caeruleum)为研究对象,通过人工授粉和去除髯毛实验对其交配系统和退化雄蕊上黄色髯毛的作用进行了初步研究,以探讨蜜导对于蓝翠雀花雌雄繁殖适合度的影响.结果发现,蓝翠雀花自交亲和,但其雌雄异熟和雌雄异位相结合的花特征完全避免了自动自交,因此该物种是专性异交植物,其传粉过程需要传粉者协助才能完成.与对照相比,去除髯毛处理显著降低了花粉的输出总量,但坐果率和结籽数并没有显著降低.我们的研究结果表明,蓝翠雀花退化雄蕊上的髯毛确实起到了蜜导的作用,但蜜导的存在主要提高了该植物的雄性繁殖适合度,表明雄性适合度的繁殖成功在蓝翠雀花的花进化过程中具有重要的作用,但这一结果仍有待在更多的居群中做进一步的验证.

Effects of the yellow barbs of the staminodes on reproductive success of Delphinium caeruleum (Ranunculaceae)

Nectar guides are special floral structures that are assumed to attract and/or direct pollinators towards a concealed nectar reward.Nectar guides are commonly found in many angiosperm plants,especially entomophilous flowers,but their functional significance and impacts on the reproductive success of plants are poorly understood.For example,Delphinium caeruleum of the family Ranunculaceae possesses two barbate staminodes,between which is the nectar entrance.To test the effects of these barbs on male and female fitness,we experimentally investigated the effects of barb removal on seed production and pollen exportation of D.caeruleum at the Haibei Station of Qinghai Province.Our results showed that flowers of D.caeruleum were dichogamous and herkogamous,which prevented autonomous selfing in this species.The mating system of D.caeruleum belongs to obligate xenogamy and thus pollinators are necessary for the successful pollination.Compared to control flowers,the number of pollen grains exported was reduced significantly after removing the barbs,but fruit set and seed number was not affected.Our primary results indicate that the barbs on the staminode act as nectar guides,which improve the male fitness of D.caeruleum,but have little effect on female fitness.Our results suggest that selection through male fitness might have played an impor-tant role in the floral evolution of D.caeruleum at our study site.These results need to be further investigated at a larger number of sites to evaluate selection mechanisms on floral traits of D.caeruleum.