荒漠短命植物小疮菊的繁育系统及其生态适应意义

Breeding System of Desert Ephemeral Garhadiolus papposus in Relation to Ecological Adaptation

小疮菊(Garhadiolus papposus)是准噶尔荒漠中常见的、具短寿命花的菊科(Asteraceae)一年生短命植物。对小疮菊的花部特征、传粉特性和繁育系统的观测结果表明,头状花序中的3类小花在花部特征上均存在不同程度的差异,说明小疮菊多态果实在小花发育过程中就已完成分化;传粉昆虫的访花高峰期与花序开放持续时间、花粉活力最高时期和柱头最佳授粉期高度吻合,从而使其在短时间内完成传粉过程以保障繁殖成功;该物种繁育系统属于兼性自交繁育系统。在准噶尔荒漠环境中,小疮菊可在传粉条件受限时,通过自主自花授粉机制来进行繁殖保障;在传粉条件正常时,通过集中开花机制来快速吸引传粉者并完成异交。该物种表现出的以上特点,避免了不可预测的环境条件对其开花、传粉过程的不利影响,是长期适应准噶尔荒漠环境的结果,对于保障其繁殖成功和种群扩大具有重要的意义。

Garhadiolus papposus was a common ephemeral Asteraceae species occurring in the Junggar Desert,with short-lived florets.To better understand how this species was adapted to its desert habitat,we studied the floral syndrome,pollination traits and breeding system of this species.The results showed that peripheral florets did not have pappus,while intermediate and central florets did.Three types of florets differed significantly in floral characteristics.These results indicated that the numbers of three morphs of achenes and their morphology had differentiated during the development period of three kinds of florets.Halictus sexnotatulus was the only floral visitor,and the duration time among insects visiting,inflorescence opening,and the highest stigma receptivity had a high degree of synchronicity,thereby ensuring that pollination was completed quickly and effectively in a short time after flowering.Furthermore,G.papposus was a facultative selfer.In the Junggar desert environment,G.papposus could not only provide reproductive assurance through autonomous self-pollination quickly when pollination conditions were limited,but also could provide the opportunities for outcrossing via concentrated flowering.The above characteristics of G.papposus avoided the adverse effects of unpredictable environmental conditions during its flowering and pollination process,which was the result of long-term adaptation to Junggar desert environment,the finding plays important role in ensuring its reproductive success and population expansion.