台灣鯨豚類粒腺體 DNA 變異分析及族群結構之研究

Abstract

台灣海域的鯨類資源、豐富且分佈廣泛，但是對鯨類的研究資料，除了早期的標本記錄及近年台灣西南海域的鯨類族群量的估算外，對族群結構並沒有任何研究報告發表。從 1993 至 1997 年來，總共蒐集 16 種鯨類，將每種各取一至三隻個體的肌肉標本，對 mt DNA 控制區域（D－loop）前半段約 400bps 進行分析，以瞭解台灣鯨豚類在此段 DNA 的變異情形及種間的差異。對樣本中數量最多的三種海豚：熱帶斑海豚（Stenella attenuata）、飛旋海豚（Stenella longirostris）及太平洋瓶鼻海豚（Tursiops truncatus , gilli) ，在東西岸各取十隻左右的樣本進行 DNA 分析，並分析樣本的外部測量形質，以瞭解各種之族群結構。 mt DNA 變異分析部分，取了台灣海域 16 種 29 隻個體進行定序，加上國外已發表的鯨種序列，共有 21 種 37 隻個體，進行鹼基對差異比較，並以相近似分析法（Neighbor－joining method）建構種間關係樹型圖。由此段序列結果發現，齒鯨亞目中除抹香鯨超科與鬚鯨亞目之 mt DNA 較為近似外，齒鯨類的種間差異皆小於與鬚鯨類的差異；喙鯨超科接著與海豚超科分開；海豚科內，虎鯨與圓頭亞科種間有明顯的差異，與海豚科其他種間分離自成一群；而海豚科內有明顯突出嘴喙的各種間關係十分混亂，無法確定。 在族群結構分析上，將所得 DNA 序列進行相近似分析法及最大儉約法（Maximum parsimony）分析。熱帶斑海豚及飛旋海豚並無明顯分群的現象，其中飛旋海豚的多樣性指數（Nucleon diversity indice）較高，故推測台灣海域飛旋海豚族群量較大；在飛旋海豚的樣本中，在東港意外發現體型較小之個體，不論是外表形態或 DNA 分析皆與台灣地區其餘個體不同，其外形大小介於日本的樣本及泰國的樣本間，故推測在西太平洋飛旋海豚體型呈連續分佈。瓶鼻海豚部分，在澎湖地區的序列與其他個體有較大的遺傳距離，推測本區族群可能為冬季隨洋流來台的族群，但在外形上並無區別。

Cetaceans have been abundant and distributed widely around Taiwan in the past. However, there were only few research on cetacean and only in taxonomy and population estimation at the southwest coastal area so far. The purpose of my thesis is to investigate (1) the phylogeny relationship among different species, and (2) population structure of few common species around Taiwan to check the correlation with geographical and morphological variation. Dr. L.-S. Chou’s research team has collected cetacean carcasses from stranding or fishery activity since 1993. In total, there were 16 species. I selected one to three muscle samples from each species for the first part of my thesis and about 10 muscle samples of three common species here, Stenella attenuata, Stenella longirostris, and Tursiops truncatus, from both east and west coasts of Taiwan for my second part of thesis. All these muscle samples were executed mt DNA sequence analysis on the control region. In addition, the morphometric measurement of the later three species was also collected for cladistic analysis. The mt DNA control region sequence of 16 local species and 5 foreign species from published gene bank were compared and structured into phylogeny tree by Neighbor-joining method. I suggest that Physeteriodea is more similar as those in the Mysticeti than other members in Odontoceti, and Ziphioidea is separated from Delphinoidea in Odontoceti. Further more, Ocinus orca showed obvious distance from the Globicephalinae, which has been stated as a distinguished group from the other species in Delphinidae. Except the taxon Globicephalids, The genetic relationship among other members of Dephinids not show any steady and distinguishable pattern. According to Neighbor-joining method and the maximum parsimony analysis of mt DNA sequence, the phenomenon of stock separation of Stenella attenuata and S. longirostris was not obvious, but slightly obvious among Tursiops truncatus. The nucleon diversity index of S. longirostris is higher than other two species. Thus, it is suggested that the population size of S. longirostris around Taiwan is either quite large or distributed continuously with great variation. One special specimen of a adult S. longirostris with the smaller body length is speculated as a mid form collected from the continuously distributed populations from Japan to Thailand. Three special Tursiops truncatus with greater genetic distance from other individuals of the same species is speculated as immigrants near Penghu Island during winter migration.