| Summary: | 碩士 === 國立臺灣大學 === 森林環境暨資源學研究所 === 100 === Mistletoes have played an important role in studying the evolution of parasitical plants in recent years. Mistletoes are almost hemiparasite and parasitize in clusters on one or many species of hosts. Mistletoes produce abundant fruits and both of their pollination and seed dispersal are mostly relied on birds. Many recent studies suggest these traits of mistletoes are resulted from the long-term co-evolution among the mistletoe, dispersers, and hosts. The clumped distribution of mistletoes is affected by two phases during the early stage of life cycle. One phase is that the seeds are affected by birds’ digestion and spreading range. The other phase is that the seeds have different host compatibility with different species or branches of hosts where they are dispersed. The mechanisms of these two parasitic phases are under-studied and the parasitic mechanisms of the mistletoes of Taiwan have been rarely reported. As a result, this research focuses on the early survival rates of seeds of Taxillus tsaii, an endemic species of Taiwan, and the effects of seed dispersers, host trees, and branch diameter.
This study was conducted in the Lianhuachih Research Center of Taiwan Forestry Research Institute (Yuchih Township, Nantou County, Taiwan), where has high density of Taxillus tsaii. I inoculated three types of seeds (coated seeds, uncoated seeds, and defecated seeds) on two classes of branch size (5-23 mm and 26-50 mm in diameter) of three host species, including Cinnamomum micranthum, Cinnamomum osmophloeum, and Camellia oleifera. I monitored the effects of different types of seeds, host species, and branch size on seeds adhesion, seeds germination, holdfast establishment, total active seed ratio, and seed survival ratio from June, 2007 to January, 2008.
Results revealed that seed germination was significantly affected by seed types. In addition, seed adhesion, holdfast establishment, total active seed ratio, and survival ratio were significantly affected by both seed types and host species. The adhered ratio greatly decreased in the coated seeds and on the branches with smooth bark. Host species did not have significant influence on germinated ratio. Defecated seeds had significantly lower germinated ratio than uncoated seeds, while coated seeds could not germinate at all. Host species was critical for holdfast established ratio, as the compatibility of Taxillus tsaii seeds differed with tree species. Haustoria of mistletoe could not establish on antagonistic species. The holdfast established ratio of digested seeds was significantly lower than uncoated seeds.
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