臺灣蜓蜥族群遺傳結構之研究

The Population Genetic Structrue of Sphenomorphus taiwanensis

郭瓊華

指導教授 ： 呂光洋博士

國立臺灣師範大學/理學院/生物學系/碩士(2001年)

摘要

台灣蜓蜥(Sphenomorphus taiwanensis)，分類上屬於有鱗目(Squamata)、石龍子科(Scincidae)、蜓蜥屬(Sphenomorphus)，為台灣特有種生物。分布於海拔2000公尺以上的山區。對於高海拔分布的物種而言，隔離的山頭可視為一個孤絕的島嶼，地理上的隔離效應可反應在族群遺傳結構上。
我們利用了粒線體上的cytochrome b及COX1序列當作分子遺傳標記，共分析9個地區、87隻個體，分別得到了56及48種haplotype類型。族群內兩個個體之間遺傳距離最大值為10.6％（cytochrome b序列）及10.4％（COX1序列），族群間兩個個體之間遺傳距離最大值為16.6％及11.2％，平均族群內遺傳距離介於0.4~9.8％及0~5.7%，族群間遺傳距離為3.2~13.9%及1.6~10.4%。此外，族群分化指數指出大部分族群間基因交流並不順暢，顯示族群分化程度明顯，隔離效應顯著，但並不符合距離隔離的模式。雪山山脈與中央山脈之間因為溪流切割所造成的隔離效應並未影響到台灣蜓蜥的族群遺傳結構。而雪山東峰地區與其他地區族群間基因交流指數值卻偏低，我們認為雪山東峰地區是一個特殊的隔離族群。
若以最儉約法則（Maximum parsimony criterion）及鄰聚法（Neighbor joining method）建構族群親緣關係，並以高的bootstrap值界定系群類型（lineage），則可發現9大系群，但系群類型與族群在地理上的分布並不完全吻合。有些地區僅出現一種系群類型，如雪山東峰、大雪山、合歡山、阿里山、南橫埡口地區。而其中雪山東峰與合歡山地區出現的系群類型僅出現於該地區，為特有的系群類型；而觀霧及太平山地區出現兩種系群類型，但兩系群所佔的比例不同；塔塔加地區出現三種系群類型；南湖地區出現四種系群類型，為多樣性最高的區域。
我們認為台灣蜓蜥的族群遺傳結構可能是受到冰河時期其族群往下移動到低海拔地區，進行基因交流；但當間冰期來臨時，可能因競爭不過低海拔的大型蜓蜥類生物，或是因不能忍受低海拔的溫度，被迫往高海拔地區移動，因此形成各種系群的基因型共同出現於同一地點。
台灣蜓蜥種內變異程度較其他物種大的原因可能是因為多次入侵、避難所效應、或者是輻射演化所造成的，並非單純因為島內地理上的隔離之後，族群再度接觸所形成的結果。

關鍵字

台灣蜓蜥 ； 族群遺傳結構 ； 高海拔生物 ； 親緣關係生物地理學

並列摘要

Sphenomorphus taiwanensis is an endemic species of Taiwan. It was distributed above 2000 m attitude. Currently, most phylogeographic studies focused on lower attitude species. To high attitude species,living in high mountains was like living in an isolation island. The geological isolation may influence the population genetic structure of S. taiwanensis. Cytochrome b (Cyt b) and cytochrome oxidase c subunit 1 (COX1) were used as genetic markers to analysis the phylogeography of S. taiwanensis. The partial sequences were determined in 89 individuals. 56 and 48 haplotype were identified. The maximum pairwise genetic distance between individuals within population was 10.6% (Cyt b) and 10.4% (COX1). The maximum pairwise genetic distances between individuals between populations were 16.6% (Cyt b) and 11.2% (COX1). The mean pairwise genetic distance within population were 0.4~9.8% (Cyt b) and 0~5.7% (COX1). The mean pairwise genetic distance between populaitons were 3.2~13.9% (Cyt b) and 1.6~10.4% (COX1). We found that the intraspecies genetic variation of S. taiwanensis was larger than other species. The gene flow index indicated that the gene flows among populations were hindered. It indicated that the differentiation level among populations was high, but was not consistent with isolation by distance model. We found the gene flows between Hsuehshan population and other populations were hindered. We thought Hsuehshan population was an special isolation population.
Phylogenetic trees were constructed by neighbor-joining (NJ) and maximum parsimony (MP) methods using S. incognitus and S. indicus as the outgroups indicated that S. taiwanensis can be separated into nine major lineages with high bootstrap value. Some lineages were allopatric, others were sympatric. The lineages’ distribution was not consistent with the geological distribution of populations. Some populations only had one lineage, included Hsuehshan, Tahsuehshan, Hohuanshan, Alishan, Yakou population. Kuanwu and Taipingshan population had two lineages, Tatachia population had three lineages, and Nanhu population had four lineages. The genetic diversity of Nanhu population was very high.
The reason of that there were high intraspecies genetic variation of S. taiwanensis may be multiple invasion or refuge effect or radiation evolution.

並列關鍵字

Sphenomorphus taiwanensis ； population genetic structure ； high attitude ； phylogeography

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