台灣產攀蜥屬之細胞遺傳研究

A Cytogenetical Study on the Genus

林鈺婷(Yu-Ting Lin)

指導教授 ： 陳世煌

國立臺灣師範大學/理學院/生命科學研究所/碩士(2006年)

摘要

台灣產攀蜥屬目前紀錄有斯氏攀蜥、短肢攀蜥、牧氏攀蜥、呂氏攀蜥和黃口攀蜥五種。前人利用形態、粒線體RFLP、12s rRNA去進行親緣關係的分析，發現變異大，但無法判定是否有隱藏種。細胞遺傳學分面，染色體資料的建立將可彌補形態分類的不足，並提供系統演化方面的另一有用的證據，本研究以染色體的核型來看台灣地區攀蜥屬蜥蜴演化親緣關係，推測染色體可能的演化方向，並可藉由核型異同得知是否仍存有隱藏種。
本研究共獲得七種台灣產攀蜥屬蜥蜴的核型資料，且經由比對發現兩個隱藏種的存在，即攀蜥sp. 1分布於台中南投低海拔山區，2N = 44 + ZZ/ZW，和攀蜥sp. 2分布於雪山山脈沿線，2N = 36。性別決定機制除攀蜥sp. 1外，其餘都未發現有性染色體存在。
在C-顯帶方面，因染色結果不佳未列入討論。
在NORs方面，台灣產攀蜥屬蜥蜴均只有一對，其中斯氏攀蜥位於第18對；短肢攀蜥位於第18對；牧氏攀蜥位於第13對；呂氏攀蜥位於第13對；黃口多稜攀蜥位於第21對；攀蜥sp. 1位於第14對；攀蜥sp. 2位於第17對。
在G-顯帶方面，大部分相對長度較長的染色體上都可發現不同形式的色帶位置，比較相似度短肢攀蜥、牧氏攀蜥、呂氏攀蜥與攀蜥
sp. 2第1、2對染色體為同源，推測有較高親緣關係；而其中的短肢攀蜥與攀蜥sp. 2又為此四種中親緣最近。而其中的短肢攀蜥與攀蜥sp. 2又為此四種中親緣最近。
台灣地區攀蜥染色體演化方面，提出兩個假說；1、融合假說為2N = 46為原始核型經染色體接合使2N數目逐漸減少，雙臂染色體數目逐漸增加形成台灣現生物種的核型；2、斷裂假說為2N=36原始核型經斷裂使染色體數目逐漸增加。以目前證據:攀蜥的形態特徵、NORs-標記染色體，以及粒線體12S rRNA，均比較支持融合假說。台灣地區七種攀蜥可分為斯氏攀蜥群:斯氏攀蜥和攀蜥sp. 1，與多稜攀蜥群:黃口多稜攀蜥、牧氏攀蜥、呂氏攀蜥、短肢攀蜥和攀蜥sp. 2；這兩群互為姊妹群。

關鍵字

攀木蜥蜴 ； 細胞遺傳 ； 染色體

並列摘要

Five known species of Japalura lizards are found in Taiwan, including J. swinhinis, J. brevipes, J. makii, J. luei, and J. polygonata xanthostoma. Great variation have been found among inter- and intra- species, however, no cryptic specie can be detected based on their morphologies, mitochondria RFLP and 12S rRNA except for the chromosome data. Cytogenetic analysis is proved to be useful in establishing animal phylogeny, especially in the identification of Japalura. The present study focus on building reconstructing the phylogenetic relationships of all Japalura including new cryptic species found in Taiwan via cytogenetical approaches.
Seven species including two new species of Japalura lizards from Taiwan were successfully karyotyped. One new specie is Japalura sp. 1 distributed in the low mountains in Taichung and Nantou Counties, another is Japalura sp. 2 distributed in the Hsueshan Mountain Range. Chromosome numbers of Japalura sp. 1 and Japalura sp. 2 are 2N = 46 and 36, respectively. The sex-determining mechanism of J. sp. 1 is ZZ/ZW type, and the others have no sex chromosome.
The C-bands of chromosomes in all Taiwanese Japalura lizards studied are not successfully stained thus is not included in the present study.
There is only one pair of Ag-NORs in the karyotypes that are located at the distal end of the 18th pair in Japalura swinhonis and J. brevipes, the 13th pair in J. makii and J. luei, the 21th pair in J. p. xanthostoma, the 14th pair in J. sp. 1 and the 17th pair in J. sp. 2.
The macrochromosomes of all taxa showed remarkable G-bands that are species specific. Karyotypic patterns among four out of seven species, Japalura brevipes, J. makii, J. luei and J. sp. 2, are relatively similar, especially in the 1st and 2nd pairs of chromosomes, that infers the close relationship among these four species. Japalura brevipes and J. sp. 2 have more similar banding patterns and are more closely related.
Two hypothesis about evolutions of the genus Japalura from Taiwan are proposed according to cytogenetic analysis. The fusion hypothesis proposed the present karyotypes with low diploid chromosome numbers and high biarmchromosome numbers were derived from a primitive karyotype with 2N = 46 and all telocentric chromosomes by Robertsonian fusions, while the fission hypothesis derived from a primitive karyotype with 2N = 36 that are suspected to Robertsonian fissions to form the present karyotypes. All the morphological data, the ribosomal 12S rRNA, and the present NORs-carrying marker chromosomes support the fusion hypothesis and against the fission hypothesis. In summary, the Japalura species in Taiwan can be separated into two sister clusters: the Japalura swinhonis group (J. swinhonis and J. sp. 1) and the Japalura polygonata group (J. p. xanthostoma, J. makii, J. luei, J. brevipes, and J. sp. 2).