鳞叶龙胆雌蕊先熟和雄蕊先熟适合度比较

Comparison of Fitness between Protogyny and Protandry Flowers in Gentiana squarrosa (Gentianaceae)

对青藏高原东缘早春开花物种鳞叶龙胆(Gentiana squarrosa)雌蕊先熟和雄蕊先熟的适合度进行了比较.试验表明,雌蕊先熟花寿命较长、花粉胚珠比低、投资在雌蕊生产上的资源较多、花朵较小,符合自花授粉特征.雄蕊先熟花寿命较短、花粉胚珠比高、投资在雄蕊生产上的资源较多、花朵较大,符合异花授粉特征.初花期,居群中以雌蕊先熟为主,未发现访花昆虫,自交率较高.盛花期,居群中以雄蕊先熟为主,发现昆虫访花(主要有蝇类、蜂类和蚂蚁),异交率高.但盛花期访花昆虫并没有区别对待两类花,进一步试验发现来源于雄蕊先熟的花粉在两类花柱头上占有的比例均最高,且在盛花期两类花均有较高的异交率.无论在自然还是人工补充授粉条件下,雌蕊先熟种子数目较雄蕊先熟显著增加.表明雌蕊先熟倾向于将资源投资在种子生产,雌性适合度高.雄蕊先熟倾向于将资源投资在花粉生产和花粉散布,雄性适合度高.研究结果对于揭示青藏高原物种适应机制提供案例.

We conducted field and laboratory experiments to examine the fitness of protogyny and protandry flowers in Gentiana squarrosa. Our results demonstrated that protogyny flowers have high selfing rate with longer life span,low pollen/ovule ratios,high female mass/male mass ratios,small flowers. However,protandry flowers have high outcrossing rate with shorter life span,high pollen/ovule ratios,low female mass/male mass ratios,large flowers. There are high density of protogyny flowers during early flowering,whereas high density of protogyny flowers are found during peak flowering. Both protogyny and protandry flowers have high insect visitation rate during peak flowering. More pollens from protandry flowers located on stigma of both flowers during peaking flowering. In addition,protogyny flowers produce more seeds than protandry flowers under nature pollination and hand-supplemented pollen. This suggest protandry flowers have high male fitness,whereas protogyny flowers have high female fitness. Our results suggest that Gentianaceae species use different strategies to respond to extreme environment of the Tibetan Plateau.