臺灣博碩士論文加值系統

短尾鼩（Anourosorex squamipes）為一屬一種的食蟲目動物，分佈在由越南至緬甸到中國大陸的四川省，以及臺灣的中高海拔山區，呈現斷續型分佈。臺灣的短尾鼩為一亞種，即山階氏鼩鼱（Anourosorex squamipes yamashinai）。本研究的目的在探討臺灣島內各地的短尾鼩族群之遺傳分化現象，以及臺灣和中國大陸短尾鼩族群呈現不連續分佈，其遺傳組成的變化，藉此推估二大族群分離的時間以及可能原因。
本研究中共收集到臺灣19處山區中短尾鼩78隻，並取得中國大陸四川省南充市8隻以及綿陽市2隻短尾鼩的肝組織。以自行設計之引子進行PCR反應增幅粒線體細胞色素b片斷後定序，得到全部樣本之部分序列737 bp。此外，為解釋臺灣和大陸族群的演化關係，選取合歡山地區5隻個體和中國大陸綿陽市2隻個體定出其細胞色素b區域完整序列1140 bp。部分序列之親緣分析結果顯示，臺灣地區短尾鼩粒線體細胞色素b序列分屬於28種單型（haplotype），單型間具有43個多型性位點。親緣關係樹之分析結果顯示臺灣地區族群與大陸四川地區族群的遺傳距離有很大的差距；且臺灣短尾鼩族群被分成南、北二大群，此二群距大陸四川族群的遺傳距離幾乎相等。有7個辨識位點（diagnostic site）可用以分隔此二群。此外，臺灣島內族群的單型多樣性指數（h）與族群分化指數（FST）均相當高，顯示臺灣短尾鼩族群的分化顯著，AMOVA（analysis of molecular variation）檢定亦支持此一結果。
完整序列的分析中，臺灣島內族群和中國大陸四川族群的遺傳距離約6％，屬於種內的差異。若以分子時鐘理論推估分群的時間點，顯示臺灣族群約在72萬年前與大陸族群分離，而臺灣島內南北二族群則約在19萬年前分離。此一結果顯示臺灣短尾鼩族群應屬一次入侵，可能在古德冰期海退時由大陸進入臺灣，於西部平原開始廣泛分佈，後因冰河期結束，族群量銳減，經歷瓶頸效應後，二不同小族群在中高海拔山系快速擴散，因山脈的阻隔而形成南北二群並獨立演化。

Anourosorex squamipes, which is the monotypic species in the genus Anourosorex, is distributed from Tonkin, through Burma to Szechuan, China and Taiwan, showing a disjunct distribution pattern. The Taiwanese form was described as a subspecies A. squamipes yamashinai and occurs in the mountainous areas of Taiwan. The purpose of my study is to investigate the genetic variation within Taiwan population and compare the divergence with disjunct population in Mainland China. Moreover, I will try to explain the possible process and divergence time that caused the isolation.
Liver tissues were obtained from 78 individuals who were collected at 19 localities in Taiwan. Those of 8 individuals from Nan-Chung city and 2 individuals from Main-Yang City in Szechuan province were prepared also. The cytochrome b fragment was amplified using PCR with two primers designed newly. The partial sequences (737 bp) of all specimens from Southwestern China and Taiwan were successfully determined. The complete sequences (1140 bp) of cytochrome b gene were also determined from 5 specimens of Mt. Houhuan in Taiwan and 2 specimens of Main-Yang City in Szechuan province. Those complete sequences were used to explain the evolutionary relationship between two populations of Taiwan and Southwestern China. In a result of phylogenetic analysis of partial sequences, 28 haplotypes were identified with 43 variable sites of Taiwan population. The results of phylogenetic trees were indicating that Taiwan population distinctly diverged from Southwestern China population and 28 haplotypes in Taiwan were clustered into two groups (Northern and Southern groups). In addition, there were 7 diagnostic sites could be used to distinguish both groups of Taiwan. The genetic distances between Northern group in Taiwan and Southwestern China population was almost similar to that between Southern group in Taiwan and Southwestern China population. Furthermore, the haplotype diversity (h) and fixation index (FST) were revealed that the divergence would be significantly high within Taiwan population. This result was supported by AMOVA test also.
In a result of analysis of complete cytochrome b gene sequences, an intraspecies variation (6%) was indicated from the genetic distance between Taiwan and Southwestern China population. Analysis of divergence time based on molecular clock theory was revealed that Taiwan and Southwestern China population was separated at 0.72 Mya and the two groups of Taiwan population were separated at 0.19 Mya. From these data, the invasion of A. squamipes from continent to Taiwan might have been occurred once. The population of A. squamipes might have reached at the western area of Taiwan during the Günz glacial period and then been distributed into Taiwan. After glacial period, the population could have been reduced, and took refuge to the middle-elevation of mountainous area, with the "bottleneck effect". So, the two groups could have been isolated by topography of Taiwan and evolved independently.

Chinese abstract..........................................................................I
English abstract........................................................................III
Introduction..............................................................................1
Materials and Methods
1. Sampling................................................................................4
2. DNA extraction, amplification, and sequencing....................5
3. Phylogenetic analysis.............................................................7
4. Population genetics................................................................8
5. Estimation of divergence......................................................11
Results
1. Sequence analysis of Taiwan and China populations...........12
1) Sequence variation...............................................................12
2) Molecular phylogeny and phylogeography..........................13
3) Divergence within Taiwan population.................................15
2. The estimation of divergence time among Taiwan and
China populations................................................................17
Discussion
1. Phylogeographic variation of Anourosorex squamipes
of Taiwan and Southwestern China populations..................19
2. Molecular phylogeny of Anourosorex squamipes
between Taiwan and Southwestern China populations........23
References...............................................................................29
Table contents.........................................................................35
Figure contents.......................................................................36
Appendix content...................................................................55
Author’s information.............................................................68

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