片断化生境中滇桐传粉生物学和繁育系统

Pollination biology and breeding system of Craigia yunnanensis in fragmented habitat

通过野外观察和人工授粉试验方法,对云南省文山州西畴县法斗分布区片断化生境中濒危植物滇桐(Craigia yunnanensis)的传粉生物学特征和繁育系统进行研究。结果表明:滇桐每个聚伞花序有2～9朵两性花,单花花期为3～4d,单花雌雄蕊在时空上有一定的隔离;杂交指数(OCI)>4,花粉-胚珠比(P/O)为1381±53;有效传粉昆虫为大头丽蝇(Chrysomyia megacephala);同株异花授粉结实率低;滇桐的繁育系统属于异交为主,部分自交亲和,传粉过程需要传粉者;自然状态下滇桐的座果率(56.67%±3.85%)和结籽率(6.26%±0.75%)均较低,而异株异花授粉均可显著提高座果率及结籽率(P<0.01),这与当前片断化生境中传粉昆虫少、效率低下等有关,表明生境片断化正在影响滇桐植株的早期生殖成功。

By the methods of field observation and artificial pollination, this paper studied the characteristics of pollination biology and breeding system of endangered species Craigia yunnanensis in the fragmented habitats of Fadou distribution area, Xichou County of Yunnan Province, Southwest China. Each cyme of the C. yunnanensis had 2-9 hermaphroditic flowers, and the lifespan of a single hermaphroditic flower was approximately 3-4 days. There existed certain temporal isolation （dichogamy） and spatial isolation （herkogamy） between the pistils and stamens of each hermaphroditic flower. The outcrossing index （OCI） was 〉4, and the ratio of pollen to ovule （P/O） was 1381±53. The most frequent and effective pollinator was Chrysomyia megacephala. The fruiting rate of geitonogamous pollination was rather low, and thus, the breeding system of C. yunnanensis was mainly belonged to outcrossing, with partial selfcompatibility, and the pollinator insects were essential. Both the fruit-setting ratio and the seed-bearing ratio under natural conditions were low as 56.67%±3.85% and 6.26%±0.75%, respectively, whereas artificial xenogamous pollination could significantly promote the fruit-setting and seed-bearing ratios （P〈 0.01）. In the fragmented habitats, the pollinators were lesser, and the pollination efficiency was lower, suggesting that habitat fragmentation affected the early stage reproduction process of C. yunnanensis plants.