台灣水韭棲地之生態因子及其族群遺傳之研究

The study on the ecological factors of habitats and the population genetics of Isoetes taiwanensis

黃鈞蕙

指導教授 ： 張永達

國立臺灣師範大學/理學院/生物學系/碩士(2001年)

摘要

陽明山國家公園內的夢幻湖長期以來一直是台灣水韭唯一的自然棲息地，然而夢幻湖漸漸演替成沼澤形態的生態系，且陸生物種有加速入侵的趨勢，嚴重壓縮台灣水韭的生長空間。
夢幻湖因降雨量大、有出水口導致湖水的水位變動很大，推測當浚深區水位達20公分上下時出水口不再出水。夢幻湖的氣溫、光量隨著不同季節而變動；其因常常有霧，一天光量大小變動極大，然而其光質分析與平地無顯著差異，陰天與晴天的光質比較也沒有顯著差異，然棲地之生態因子與台灣水韭生長的相關性，有待進一步探討。此外，在冷水坑人工溼地的台灣水韭族群以樹林下的生長狀況最好，可移植更多台灣水韭於當地種植；竹子湖種植的台灣水韭族群，因為有藻類共同競爭陽光的問題，仍在模擬台灣水韭最適生長狀況。
夢幻湖的植被物種分布，浚深區與湖區的狹葉泥炭蘚的量並無顯著差異。以夢幻湖空照圖看植被分布，並與民國90年的空拍圖比較，台灣水韭生長的範圍有被針藺壓縮的趨勢；若以穿越線調查植被，以狹葉泥炭蘚出現頻率最高，在浚深區亦為出現量最多，然而在湖區的穿越線出現量最多的為針藺，其次為台灣水韭與水毛花；樣區植被變遷，台灣水韭與狹葉泥炭蘚在樣區的分布面積比例下降，莩藎與水毛花的面積分布比例提高，然而是否為植被演替或為季節性消長，仍有待後續研究。
在浚深區與湖區的台灣水韭生長狀況比較，浚深區的台灣水韭葉片較長，而湖區的葉片數較多，此為不同區的環境不同導致，然而台灣水韭葉片面積與植株密度並無顯著差異，因此民國81年陽明山國家公園處理的浚深工作對擴展台灣水韭棲地是有利的。
在台灣水韭族群遺傳研究方面，以夢幻湖與冷水坑的族群同功異構酵素檢測二者間的遺傳距離為0.021，顯示兩區域的族群類似，經合併族群檢測哈溫平衡，顯示台灣水韭族群沒有在哈溫平衡的狀態下。

關鍵字

台灣水韭 ； 棲地 ； 族群遺傳 ； 生態因子 ； 光量 ； 光質 ； 夢幻湖 ； 演替

並列摘要

The Dream Lake in Yangmingshan National Park is the only natural habitat of Isoetes taiwanensis. The succession took place in Dream Lake so that it has gradually turned into the ecosystem of swamp, and the land plants in Dream Lake have spread more widely. As a result, the habitat of Isoetes taiwanensis has severely been affected .
Two factors- the heavy rainfall in Dream Lake, and an outlet located in the southeast of Dream Lake have resulted in the tremendous variation of water level in Dream Lake. It is inferred that when the water level in the dredged area of Dream Lake is about 20cm high, there is no outflow from the outlet. The temperature and the amount of light in Dream Lake vary from season to season. Since the Dream Lake is usually shrouded in mist, the amount of light in one day fluctuates tremendously. Although there is no statistically significant difference not only between Dream Lake and the plain, but also between sunny days and misty days, it still can’t be concluded that the ecological factors of the habitat and the growth of Isoetes taiwanensis are completely unrelated. Further more, a comparison was made among different areas in the artificial wetland of Lan-Shue-Ken concerning the growth condition of the Isoetes taiwanensis, the Isoetes taiwanensis grows best in the area under the shade of trees. Therefore, more liverworts have been transplanted. The growth condition of Isoetes taiwanensis population in Bamboo Lake is characterized by the fact that there are some algae competing with Isoetes taiwanensis for light, and now the most suitable growth condition is still being simulated.
In this study, there are four findings of the distribution of plant species in Dream Lake, there is no statistically significant difference between the undredged area and dredged area of Dream Lake in dried weight of Sphagnum cuspidatum. Next, after comparing the aerial photography of Dream Lake in this study with that in 2001, the superficial measure of Isoetes taiwanensis has decreased, but the superficial measure of Eleocharis congesta has increased. Third, according to the results derived by the line transect sampling, Sphagnum cuspidatum, occurs most frequently and is the most abundant species in dredged area of Dream Lake. In the undredged area of Dream Lake, Eleocharis congesta is the most abundant species; Isoetes taiwanensis and Schoenoplectus mucronatus are second in abundance to Eleocharis congesta. According to the conversion of species in the sampling area in this study, the superficial measure of Isoetes taiwanensis and that of Sphagnum cuspidatum have decreased, but the superficial measure of Sphaerocaryum malaccense and that of Schoenoplectus mucronatus. Further study is needed to investigate whether such a conversion has resulted from ecological succession or from seasonal variation.
When the growth condition of Isoetes taiwanensis in the undredged area and dredged area in Dream Lake is compared, the length of the leaves of Isoetes taiwanensis is longer in the dredged zone and the number of leaves of one liverwort is larger in the undredged area. This phenomenon is caused by different environment of the lake. However there is no significant difference between the undredged area and the dredged area in terms of the superficial measure of one leaf and the density of Isoetes taiwanensis. Therefore, the work to dredged in Dream Lake by Yangmingshan National Park in 1992 was more advantageous to the expansion of the habitat of Isoetes taiwanensis.
There are two major findings regarding the population genetics of Isoetes taiwanensis. Isozyme of the subpopulations in Dream Lake and Lan-Shui-Ken were tested. The genetic distance between the two subpopulations is 0.021, meaning that the two subpopulations are similar to each other. When the two subpopulations were pooled, and the Hardy-Weinberg equilibrium was tested, the population of Isoetes taiwanensis is not in the Hardy-Weinberg equilibrium.

參考文獻

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