菊科入侵植物三叶鬼针草的繁殖特征及其与入侵性的关系

三叶鬼针草(Bidens pilosa)是一种危害严重的菊科入侵植物。通过实验观察和人工控制套袋等方法, 对其花序开花动态、花粉胚珠比 (P/O)、自交亲和性、花粉活力、访花昆虫和种子 (瘦果)的萌发率等与繁殖相关的特征进行了研究, 探讨了这些繁殖特征与入侵性的关系。三叶鬼针草在10-11月开花, 单个花序的花期约为5-6天。每小花的花柱基部有圆筒状的蜜腺环绕。单个花序内可自交亲和, 自交结实率和花粉活力均较高, 其P/O值为1 7 54.1 2±29 .8 7。主要访花者为灰蝶科(Lycaenidae)、粉蝶科(Pieridae)和茧蜂科(Braconidae)昆虫。三叶鬼针草所具有的灵活交配机制是其入侵成功的重要因素。此外, 三叶鬼针草结实量大、种子产生迅速且适于传播, 以及种子萌发范围广和短期快速萌发等特性也增强了其入侵性。

Reproductive Traits Associated with Invasiveness in Bidens pilosa (Asteraceae)

Bidens pilosa is one of the noxious invasive weed in Asteraceae. We studied reproductive traits of this species such as phenology of capitulum, ratio of pollen to ovule (P/O), self-compatibility, pollen viability, visiting insects and germination potential of seed (achene) by experimental observation and bagging treatment in order to assess the association of these reproductive traits with invasiveness. B. pilosa flowered during October to November . The lifespan of a single capitulum was approximately 5 to 6 days. The cylindraceous nectary encircled the stylar base of each floret. Bagged capitulum showed high seed set potential which means self-compatibility and high pollen viability during flowering. The P/O ratio was 1 754.12±29.87, which suggests that the breeding system was facultative xenogamy. The main floral visitors were insects of Lycaenidae, Pieridae and Braconidae. Our results associated with those of others show that the reproductive traits of a versatile mating system of self- and cross-pollination in B. pilosa are important factors attributing to invasion of this weed. Moreover, other traits, such as the high production of achenes (seeds ), high germination percentage and rapid germination rate, as well as high dispersal capability of achenes, might contribute to the species’ successful invasive capability too.