Study On The Adaptive Significance Of Flexistyly In Amomum (Zingiberaceae)

Flexistyly is a novel flowering strategy, unique and'active'floral dimorphism achieved by both changing the position of the style and separating the maturation of male and female organs in different times, lately found in Zingiberaceae plants. Base on the pollination ecology of Amomum species, this research is going to try to understand the evolutionary and ecological significance of flexistyly from the perspective of mating system.Populations of ginger plants Amomum have two reciprocal and dynamic phenotypes that differ in flowering behavior: (1)"cataflexistyle"individuals with the stigma held erect beyond dehiscent anther when anthesis begins in the morning and becoming decurved under the anther at noon; (2)"anaflexistyle"individuals with the receptive stigma decurved under the indehiscent anther first and moving into a reflexed superior position above the anther as it begins to shed pollen at midday. A flower lasts only one day, and the ratio of the two phenotypes in natural populations is 1:1.In this research, three species (two groups) are included——group 1 (A. maximum, A. putrescens) having flexistyly, while the group 2 (A. villosum) not. Through comparing the outcrossing rate of the two groups, we found the outcrossing rate of group 2 are significantly higher than that of group 2, that is to say the plants, with this outcrossing mechanism——flexistyly which is a most significant factor influencing the reproduction, prevent selfing and promote outcrossing. And also, we compare the outcrossing rate of"cataflexistyle"and"anaflexistyle"phenotype in the same plant, and find outcrossing rate of"anaflexistyle"phenotype all are different from that of"cataflexistyle"——though only in one population the first is significantly higer than the last.And the fruit set of the three species also are compared. The results show that: the fruit set of A. maximum are significantly higher than that of A. putrescens and A. villosum, but no difference between the two. Yet the fruit set of of"anaflexistyle"phenotype is higer than that of"cataflexistyle"phenotype, though not significant. So, there is a possibility that the anaflexistylous flowers may function more as females and cataflexistylous flowers more as males. In all, flexistyly, the temporal separation of male and female functions in flowers with two genetically, temporally reciprocal morphs of equal numbers, is understood to come from synchronous dichogamy and is heading towards dioecy.