被子植物雌全同株性系统:系统演化、性表达与进化意义

雌全同株是指雌花和两性花共同发生在同一植株上的性表达形式。作为被子植物从雌雄同花(两性花)向雌雄同株异花进化的一个重要阶段,雌全同株性系统在减少昆虫对雌性的取食和伤害、提高异交率以减少近交衰退、减少雌/雄功能干扰、提高雌/雄性功能间资源分配的灵活性,以及吸引传粉者等方面具有重要的进化适应意义。根据APG III分类系统,雌全同株性系统在被子植物木兰分支(magnoliids)的短蕊花科、单子叶植物分支(monocots)的天南星科和禾本科,以及核心真双子叶植物分支(core eudicots)中的菊科、苋科、唇形科和石竹科等23科中均有报道,且以菊科植物中最多。雌全同株植物不同类群的雌花和两性花在位置、形态、大小及开花时间等性表达特征上表现出多样化,且这些特征不仅受遗传因子的调控,还受可获得资源(如营养、光照、温度和水分等条件)的制约。该文针对我国对雌全同株性系统的研究还相对较少的现状,重点对具雌全同株性系统的类群在被子植物中的分布与系统演化、性表达与环境的关系等方面进行了分析与总结,并对有关其进化适应意义的5个假说进行了介绍和评价,对今后的研究方向进行了展望,以期为推动我国对被子植物雌全同株性系统的进化式样与机制研究提供理论资料。

Gynomonoecy in angiosperms: phylogeny,sex expression and evolutionary significance

Gynomonoecy is the mode of sex expression in which female and bisexual flowers occur on the same plants; it is an important step in the evolution of monoecy from hermaphroditism in angiosperms. The sexual system of gynomonoecy is considered to play several important roles, including reducing herbivore damage to pistils, reducing inbreeding depression by favoring out-crossing and pollen-pistil interference, enhancing the flexibility of resource allocation to male and female functions in two flower types, and attracting pollinators. According to the classification of APG III system, gynomonoecy occurs in about 23 families in angiosperms including Lactoridaceae in magnoliids, Araceae and Poaceae in monocots, and Asteraceae, Amaranthaceae, Lamiaceae and other families in eudicots. Gynomonoecy is most common in Asteraceae. Female and bisexual flowers from different gynomonoecious taxa show diversified sex expressions, such as their position in inflorescence, morphs, size and flowering time. These traits are regulated not only by genetic factors, but also by resource availability (e.g., nutrition, light, temperature, and moisture conditions). Because reports on gynomonoecy in China are rare, this paper emphasizes our analysis and summary of the phylogeny of gynomonoecious taxa and their evolution in angiosperm and the relationship between their sex expression and environmental conditions. In addition, five hypotheses on the evolutionary significance of gynomonoecy are introduced and evaluated in this paper. Finally, we discuss prospects for further research in this topical area. Our purpose is to provide a theoretical framework for research on evolutionary patterns and mechanisms of gynomonoecy for angiosperms in China.