中国特有的两种同域分布凤仙花属植物的传粉生物学研究

Pollination biology of two Chinese endemic and sympatric Impatiens ( Balsaminaceae )species

关键词:  黄麻叶凤仙花, 金凤花, 传粉生物学, 同域分布, 繁育系统, 传粉综合征

Key words:  Impatiens corchorifolia, Impatiens cyathiflora, pollination biology, sympatric distribution, breeding system, pollination syndromes

摘要:

中国是凤仙花属物种多样性分布中心之一,存在着大量的特有和同域分布现象。为更好地理解同域分布近缘种的传粉综合征分化以及传粉昆虫资源分配问题,该文以中国特有种黄麻叶凤仙花(Impatiens corchorifolia)和金凤花(I. cyathiflora)为研究对象,通过野外调查和实验完成传粉生物学的相关研究,比较分析了这两个种的开花物候、花形态结构、传粉昆虫的种类及访花行为和人工授粉实验等方面的异同。结果表明:(1)两种凤仙花的花距不同,花距的长度与花蜜量呈正比,但与花蜜含糖量无关。花距类型决定了两种植物的传粉昆虫种类的分化。具短花距的黄麻叶凤仙花的花蜜含量为(4.57±1.43)μL,花蜜糖含量为(45.48±2.28)%,由蜜蜂和胡蜂为其传粉。拥有长花距的金凤花的花蜜含量为(10.15±3.28)μL,花蜜糖含量为(46.12±1.48)%,除蜜蜂和胡蜂传粉外,天蛾和熊蜂也为其传粉昆虫。(2)两种植物虽然共享3种传粉者,但表现为明显的错峰访花,传粉行为和花通道的差异决定了传粉者携带花粉的部位不一致。(3)繁育系统实验表明,两种植物均表现出明显的种间杂交障碍和异花授粉偏好性。因此,花距形态差异显著导致了传粉综合征分化明显和传粉昆虫行为各异。两种植物授粉均需要传粉昆虫且均无法自花授粉,呈现异交优势; 并且可以通过部分传粉昆虫、花形态差异以及杂交不亲和等情况维持生殖隔离。该研究结果为理解凤仙花属的传粉综合征、同域分布近缘物种传粉昆虫资源分配等方面提供了新资料。

Abstract:

The genus Impatiens exhibits some varied floral features with a dichogamous reproductive system, in which pollination biology plays a key role in speciation and adaptive evolution. China is one of the centers of Impatiens species, including a large number of endemic and sympatric distributions, but there are few data on their pollination biology. Comparative pollination biology of two Chinese endemic and sympatric species, Impatiens corchorifolia and I. cyathiflora, were investigated, including flowering phenology, floral features, pollinators, behavior of pollinators, and as well as breeding systems. The results were as follows:(1)Morphology of spur was varied in two species, which played a key role in different floral syndromes. The spurs in I. corchorifolia and I. cyathiflora could produced a similar nectar sugar content,(45.48 ± 2.28)% and(46.12 ± 1.48)%, respectively. They could share two pollinators, Apis cerana and Vespa. However, the short spur in I. corchorifolia produced less amount of(4.57 ± 1.43)μL nectar while the long spur in I. cyathiflora yielded more nectar content of(10.15 ± 3.28)μL. And then, the latter also could be pollinated by the other insects including one species of Macroglossum and two species of Bombus.(2)The behavior of the common pollinators shared in I. corchorifolia and I. cyathiflora were obviously distinguished by their staggered flower visits and differential sizes of flower channels for visitors with inconsistent positions of pollens carried.(3)Breeding system experiments showed that species possessed obvious hybridization barriers and obvious cross-pollination. Thus, significant differences in spur morphology lead to distinct pollination syndrome differentiation and different pollinator behavior. Both species prefer cross-pollination to self-fertiliation, which greatly depend on the effective pollinators. Reproductive isolation could be maintained by different flower visiting behavior of shared pollinators, differences in floral morphology, and heterozygous discordance. It provides new evidence for a better understanding the relationships between pollination syndrome, pollinators behavior, and cross-breeding stystem in Impatiens.