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  • Title: Blooming characteristics and breeding system of an invasive plant Gaura parviflora.
    Author: Guo YY, Liu LC, Meng W, Wang XY, Yao HR, Li LJ.
    Journal: Ying Yong Sheng Tai Xue Bao; 2023 Jun; 34(6):1517-1524. PubMed ID: 37694413.
    Abstract:
    The invasiveness and dissemination of exotic species are strongly influenced by its sexual reproduction characteristics, including blooming characteristics and breeding system. Exploring the association of these sexual reproductive traits with invasiveness would be helpful for revealing the mechanism of its successful invasion. We examined the blooming characteristics and breeding system of Gaura parviflora based on field observations, out-crossing index (OCI) estimation, and hand-pollination experiments. The results showed flowering duration of the G. parviflora population (flowering period) was short (more than 3 months). The life span of single flower (floral longevity) was 40.46 h. Its flower diameter was 3.99 mm. Over seven flowers in bloom per inflorescence and most individuals often bloomed synchronously, which showed a 'mass-flowering pattern'. The changing trend of pollen and stigma vitality was relatively similar, but the duration of stigma vitality was 2 h longer than that of pollen. The stigma and the anthers were close to each other at the initial flowering stage, but the stigma removed from the anthers at the full-blooming stage with the style curving downwards. Many pollinators visited flowers in late full-blooming stage, which were mainly Apis mellifera and Syrphidae spp. Their average visiting frequency was 9.8 times·m-2·h-1. The fruit set in natural pollination after emasculation treatment (insect or wind pollination) was signi-ficantly higher than that in bagged and emasculation treatment, and the treatment of emasculated and bagged with nylon net (excluding insect pollination) could also bear fruits, indicating possible existence of ambophily in G. parviflora. The results of pollen ovule ratio (P/O) mensuration, OCI estimation and hand-pollination experiments showed that its mating system type belonged to additive mixed mating system. So, its characteristics, such as smaller flower size, shorter floral longevity and flowering period, were conducive to allocating more resources to plant growth and seed development, which would help improve its total fitness. The changes of spatial position of male and female organs not only avoided interference between male and female functions, but also created opportunities for stigmas to receive outcross pollen. In addition, the 'mass-flowering pattern' was conducive to attracting pollinators. The pollination mechanism of ambophily was helpful to ensure cross-pollination. The additive mixed mating system could provide double reproductive assurance for this species. These reproductive characteristics were significant for the successful invasion and expansion of G. parviflora. 有性繁殖特征(如开花特性、繁育系统等)是影响外来植物成功入侵和扩张的重要因素,探明这些特征与入侵性的关系,有助于揭示其成功入侵的机制。本研究采用野外观察、杂交指数(OCI)估算以及人工授粉试验等方法,对外来入侵植物小花山桃草的开花特性和繁育系统进行研究。结果表明: 小花山桃草种群的开花持续时间(花期)较短(3个多月),单花开花时间(花寿命)仅为40.46 h。虽然其花径仅为3.99 mm,但每个花序同时开花数达7朵以上,且种群中的个体常同步开花,呈现出“集中开花模式”。花粉与柱头活力的变化具有较高的同步性,柱头活力维持的时间比花粉长2 h。在初开期柱头与花药的位置邻近,到盛开期花柱下弯,柱头与花药拉开空间距离。盛开期后期,有多种传粉昆虫访花,主要传粉昆虫为西方蜜蜂和食蚜蝇,平均访花频率达9.8次·m-2·h-1。去雄自然授粉(虫媒或风媒)的结实率显著高于去雄套袋的结实率,去雄套网袋(排除虫媒)也能结实,表明其可能存在风媒与虫媒并存的混合传粉机制。花粉胚珠比值、杂交指数以及人工控制授粉试验结果表明,其交配系统为互补型混合交配系统。总之,较小的花径、较短的花期和花寿命,有利于小花山桃草将更多资源分配到植株的生长和种子的发育,总适合度提高。雌雄蕊空间位置的变化既可减少雌雄功能干扰,也为异花授粉提供了机会。而“集中开花模式”有助于吸引传粉昆虫。风媒与虫媒并存的混合传粉机制有助于保障异花授粉。自交异交互补的混合交配系统,可为繁殖成功提供双重保障。小花山桃草的这些繁殖特性对其成功入侵和扩散蔓延具有重要意义。.
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