台灣地區外來種緬甸小鼠的族群遺傳結構與生物地理起源

Genetic Patterns and Biogeographic Origins of the Exotic Rodent (Rattus exulans) in Taiwan

本研究利用SSCP（single-strand conformation polymorphism）技術，分析近年發現入侵台灣之外來種緬甸小鼠（Rattus exulans）粒線體DNA單倍體基因型（haplotype）的多型性，探尋其可能來源，並檢視各基因型在花蓮縣吉安鄉的分布狀況，以推論此外來種族群的擴散模式。在粒線體DNA控制區（mtDNA control region）中，以SSCP共判別出4種單倍體基因型（Type I-IV），其中TypeI和II占大多數，且分布最廣；TypeIII和IV則較少，皆僅見於單一捕捉點。經與NCBI資料庫中的序列比對，發現TypeI與分布於泰國的序列相同，而TypeIV則與蘇拉維西的序列相近，推測入侵台灣的緬甸小鼠來自東南亞大陸及週邊島嶼區域，而由各基因型間的遺傳變異程度判斷，緬甸小鼠可能至少有2次以上的入侵史。 Mitochondria DNA (mtDNA) haplotypes were identified with single-strand conformation polymorphism (SSCP) for the exotic rodent (Rattus exulans) found in Jian Township, Hualien County, Taiwan. The objectives of this study were to examine distribution patterns of the haplotypes and to determine biogeographical origins of this exotic rat. We found four distinct SSCP haplotypes, Types I, II, III and IV, in a segment of 372 base-pairs in the mtDNA control region. Types I and II were dominant and occurred widely in the sampling area, while Types III and IV were restricted, each to a single sampling location. When the sequences of the four haplotypes obtained in this study were compared with the sequences of 32 R. exulans haplotypes available in NCBI, Type I was identical to the sequence from Thailand, Type IV differed to one sequence from Sulawesi by only one base pair. The results indicated that this species of exotic rat in Hualien might be originated from the Southeast Asia mainland and Malay Archipelago. The presence of four haplotypes suggested that there were at least two invasion events.