臺灣博碩士論文加值系統

台東蘇鐵 (Cycas taitungensis Shen, Hill, Tsou & Chen) 僅分佈在台灣東南部海岸山脈和鹿野溪中游陡峭山坡上，研究其族群生態及遺傳變異的結果顯示台東蘇鐵在人為干擾區域有年齡結構不均勻的現象，在遺傳變異上則顯示族群內變異極大，而亞族群間的分化程度低。
本研究共分兩部份，一是族群生態研究：在台東蘇鐵紅葉村自然保留區內進行台東蘇鐵的每木調查和生態研究，所獲之結果顯示成株雌雄性比略為1.7：1，結種率約45﹪，樹高與葉片數在幼期具相關性，若以樹高為指標，進行族群內的年齡結構評估，則發現中齡植株甚少，年齡結構不均勻。野外觀察資料顯示，成熟種子遭盜採殆盡，小型幼樹亦遭採集，保留區內人為干擾嚴重。
在遺傳變異方面的研究則以分子序列技術序列出細胞核核糖體DNA的ITS區域共77片斷，應用支序系統學 (Cladistics) 原理，經由比對分析序列，評估台東蘇鐵族群內的歧異度，發現此一古老物種在族群內個體間分子層次上保有極大的變異度 (π=0.17)，亞族群間並無基因分化，例如相對山坡上之亞族群，各山坡與分佈隔離之族群比較分別為FST =0.002、0.003、0.006。此高度變異的原因可能源自有性生殖的基因重組，由於台東蘇鐵的種子主要以重力及動物攜帶傳播，且為昆蟲傳粉，亞族群間無分化的幾個原因中，最可能的原因為台東蘇鐵原為連續分佈的族群，今日之隔離分佈係近代所發生，基因流傳中斷不久，兩族群間尚未有足夠的時間產生遺傳上的分化。本研究的結論是分佈在不同坡向及不同地點的台東蘇鐵在生態上呈現顯著的差異，但在遺傳上並沒有分化，微環境的不同僅影響了台東蘇鐵的生長和 (或) 繁殖，尚未影響到它的族群遺傳結構。

Cycas taitungensis is an endemic species which is restricted to the riverside along Lu-Yei River and the mountainous area at the eastern coastal range in Taiwan. The thesis composed of two parts: the first included ecological study of C. taitungensis and the second genetic variability of C. taitungensis population. In ecological study, the age structure of the population habituated in the disturbed area is unequilibriated. The genetic study showed that the nucleotide diversity within populations is high.
The enumeration measurment included (1) the amount of seed production per year, (2) one-year survival rate of seedling, (3) sex ratio and age structure and (4) the annual foliage leaf production. Three study plots and one 200-meter transect were arbitrary established in the natural reserve area. The results indicated that the field sex ratio was 1.7:1, the seed reproduction rate c.a. 45%, and one-year seedling survival rate in the range of 2-17%. Also, the numbers of foliage leaves were found positively correlated with the size of the plants. In the disturbed area, the age structure shows that the numbers of mid-age cycads were reduced, that implied the plants have been unlawfully deforested.
In the genetic variability study, internal transcribed spacer （ITS）region of ribosomal DNA from 50 individuals were amplified, cloned and 77 sequences were obtained. Based on nucleic acid information, the population phylogeny trees were constructed. An unexpected high nucleotide diversity (0.17) among the 77 sequences was detected. However, no genetic differentiation between subpopulations（FST=0.002-0.006）was found, which is in agreement with allozyme analysis. A high genetic polymorphism can be accounted for the intramolecular recombination. The seed dispersal of C. taitungensis is known by gravity and possibly by insect pollination. Since the gene flow between the plants is weak, the poor differentiation between the subpopulation may be habitat fragmentation. Besides, the effect of environment factors was more important in the ecology of C. taitungensis than in genetic variability.

目 錄
目錄 Ⅰ
圖次 Ⅱ
表次及附錄 Ⅲ
中文摘要 Ⅳ
英文摘要 Ⅴ
壹、前言 1
貳、文獻回顧 5
一、台東蘇鐵的分類地位、生育地、形態特徵及其生殖機制 5
二、蘇鐵類植物的相關研究 10
三、核糖體DNA的相關研究 13
四、族群遺傳與演化 18
參、材料與方法 20
一、台東蘇鐵的生態研究 20
（一）台東蘇鐵每木調查 20
（二）族群數量統計 20
二、台東蘇鐵族群內變異之研究 22
三、統計分析 29
肆、結果 33
一、台東蘇鐵的生態研究 33
（一）每木調查結果 33
（二）存活率估算 37
二、族群內遺傳變異之研究------------------------------------------------- 38
（一）台東蘇鐵核糖體DNA的ITS的序列的多態性 39
（二）族群內遺傳變異及亞族群間遺傳分化的分析 42
（三）親緣樹的建構 45
伍、討論 49
一、台東蘇鐵的族群生態變異之探討---------------------------------------- 49
二、台東蘇鐵族群內遺傳變異之研究-------------------------------------- 52
（一）遺傳變異的生成及維持機制----------------------------------------- 52
（二）低的族群遺傳分化，高的個體內遺傳歧異度 57
陸、結論 60
柒、參考文獻 61
捌、附錄 69

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