Mating system and stigmatic behaviour during flowering of Alpinia kwangsiensis (Zingiberaceae)

Abstract.

 Little is known about the breeding systems of tropical perennial ginger species. In this paper, we provide information about the breeding system of Alpinia kwangsiensis in Yunnan, Southwest China, specifically self-compatibility, mechanisms promoting outcrossing, and the visitation characteristics of pollinators. Populations of A. kwangsiensis have two specific phenotypes that differ in flowering behaviour: 1) “cataflexistyle” individuals in which the stigma is held erect above the dehiscent anther when anthesis begins in the morning and becomes decurved under the anther at noon and 2) “anaflexistyle” individuals in which the receptive stigma is decurved under the indehiscent anther first and moves into a reflexed superior position above the anther as it begins to shed pollen at mid-day. The stigmatic movements in the two floral phenotypes, which occur in a ratio of 1:1 in natural populations, are synchronous and correlate with the foraging behaviour of floral visitors; pollination is effected only between floral forms. Field experiments indicate that A. kwangsiensis is self-compatible and dependent upon insects for fertilization. This newly reported floral mechanism, which we have named “flexistyly,” adds to the repertoire of devices that have evolved in flowering plants to insure outcrossing.