Migration of Trochodendron aralioides (Trochodendraceae) in Taiwan and Its Adjacent Areas

昆欄樹(Trochodendron aralioides)在台灣及其鄰近地區之遷移歷史

黃星凡(Shing-Fan Huang) ； 林讚標(Tsan-Piao Lin)

《Botanical Studies》 47卷1期 (2006/01) Pp. 83-88

摘要

本文利用已發表之化石及族群遺傳資料，包括同功異構酶及葉綠體DNA片段序列變異，來推測昆欄樹遷移到台灣及其鄰近地區之可能歷史。昆欄樹之葉綠體DNA變異型(haplotype)經由比較外群植物－鐵青樹(Tetracentron sinensis)，來認定原始型及其衍生型，日本族群之變異型是最原始的，而且與台灣及琉球之變異型不同。分子時鐘顯示，日本與台灣之族群是在5.5±2.8百萬年前分化出來的，這個時間也可能是昆欄樹最初遷移到台灣之時間。至於遷移路線最有可能是由日本經由琉球而移入台灣。由於近昆欄樹之化石在亞洲只有在中國東北，日本及堪察加群島發現，推測由中國大陸遷移入台灣之可能性不高。至於現生之琉球族群，推測是由台灣遷移過去的，因為琉球在一百萬年前曾沉入到海面下，故早期移入之族群隨之消失。同時，台灣及琉球之族群具有相同之葉綠體DNA變異型，而且同功異構酶之岐異度北台灣之族群平均比琉球的族群高一倍左右，顯示出遷移方向是由台灣移向琉球。

關鍵字

葉綠體DNA ； 親緣地理 ； 台灣 ； 昆欄樹

並列摘要

A migratory history of Trochodendron aralioides was postulated by integrating the published fossil records and the data sets of chloroplast (cp) DNA and allozyme. The populations from Taiwan, the Ryukyus, and Japan were investigated. The haplotype network of Trochodendron was constructed by the computer program TCS by taking Tetracentron as outgroup to direct the haplotype network. The paper shows that Japan's populations were clearly distinguished from those of the Ryukyus and Taiwan, with Japan's being more primitive. Nine substitutions were found between Tetracentron and Japan's population of Trochodendron. Based on fossil evidence, taking 50 My (million years ago) as divergence time between Tetracentron and Trochodendron, the date of separation between Japan and Taiwan's populations can be dated to 5.5 My, and the standard error is ± 2.8 My. Given a likely temperate origin and no extant or fossil plants discovered in eastern China, the migratory route that led Trochodendron to move into Taiwan was likely from Japan via the Ryukyus. However, the ancient populations in the Ryukyus should have vanished at least once as the Ryukyus were submerged around 1.0 My. As a result, the populations now in the Ryukyu Islands were derived from Taiwan, which is exemplified by the shared haplotype of cpDNA between Taiwan and the Ryukyus and less heterozygosity in the Ryukyus compared to Taiwan based on allozyme data.

並列關鍵字

Migration ； petG-trnP ； Taiwan ； Trochodendron aralioides