臺灣產黑蒙西氏小雨蛙(Microhyla heymonsi)族群遺傳結構與親緣地理學研究

Abstract

現今生物的族群遺傳結構，都受到過去歷史事件 (地質變動與氣候變遷) 及生物特性 (物種移動能力) 等因素的影響，綜合起來形成我們現今看到的生物族群結構的樣貌。藉由研究探討物種的親緣地理學，對瞭解一個物種的自然史是極為有幫助的。兩棲類動物一般被認為是遷移能力較差的脊椎動物類群，臺灣在地形結構上相當多樣，且與鄰近地區的地理關係相當密切，這樣高度的地形岐異度以及歷史上豐富的地質事件，是否會對臺灣兩棲動物的族群遺傳結果造成影響? 因此本研究利用分布在臺灣西南及東南部，中、低海拔的黑蒙西氏小雨蛙 (Microhyla heymonsi) 為材料，探討該物種的擴散能力以及臺灣的地質事件如何塑造其親緣地理關係。 本研究利用粒線體中的cytochrome oxidaseⅠ(COⅠ)部份序列來進行族群遺傳結構的探討。從全臺25個族群、181隻樣本，成功定序出181條COⅠ序列，總長625bp，由181條序列當中可釐出48條基因型。以基因型為操作單元建構親緣關係樹。結果顯示臺灣黑蒙西氏小雨蛙可分成兩個主要的系群，分別對應中央山脈以東及以西的族群，顯示中央山脈的確是會造成東、西部族群因地理隔離的效應而產生遺傳分化的情形。以中性演化理論檢測、Mismatch distribution、Nested Clade Analysis以及貝氏天際線點圖的結果顯示，在更新世時期，臺灣黑蒙西氏小雨蛙族群經過了快速擴張的事件，提供了一個生活在亞熱帶及熱帶地區的生物，受到更新世氣候變遷影響的例子。 在本次研究中取得國外6個族群，共20個樣本進行大範圍尺度的種內遺傳分化情形探討。結果顯示，分布於東南亞不同地理區間的黑蒙西氏小雨蛙族群的遺傳分化情形相當明顯，而臺灣族群與地理位置較接近的海南、貴州、越南北部的族群在親緣關係上較為接近，顯示東南亞地區複雜的地質事件與其本身的擴散能力，對於黑蒙西氏小雨蛙的族群遺傳結構上有著明顯的影響。本次研究在國外樣本上並無取得足夠的族群以及樣本數，因此無法討論臺灣族群的來源、族群間的散佈歷程以及各族群的族群變動歷史，未來將可朝著增加樣本數，進而闡明整個大尺度分布的黑蒙西氏小雨蛙族群的演化歷史。In this study, I used Microhyla heymonsi (Anura: Microhylidae), a low to mid-altitude distributed narrow-mouth frog in Taiwan to investigate the pattern of phylogeography by using mitochondrial cytochrome oxidaseⅠ(COⅠ) gene. Meanwhile, I also discuss the phylogeographic and the population structure relationship with the historical geological events and dispersal ability of the frog in Taiwan. A total of 181 specimens were collected from 25 populations throughout the island. The results of phylogenetic tree indicated that there are two major haplotype clades in Taiwan. The variation of population genetics of these two clades correspond to the eastern and western geographical features of Central Mountain Range, respectively. Central Mountain Range is a major geographic barrier and disrupt the gene flow between eastern and western populations. Both major clades showed a significant isolation by distance effect. Historical population demography analyzed using neutrality tests, mismatch distribution and Bayesian skyline plot analyses showed that populations of M. heymonsi in Taiwan were undergone an expansion event during Pleistocene Epoch. M. heymonsi widespreads in South and Southeast Asia. The diversification of frogs among these regions is an interesting subject. Our results suggested that there was substantial genetic differentiation among populations in SE Asia. Because we did not have enough samples of populations in these areas, especially regions of southeast China, so we were unable to discuss the source population of Taiwan, the colonization sequence among populations and retrace the historical demography. If we can increase the sample sizes in distributed areas in the near future, we will be able to interpret the evolutionary history of the widely distributed species.