- 學位論文
日本絨螯蟹 ( Eriocheir japonica ) 遺傳多樣性之研究
The Genetic Diversity of Eriocheir japonica ( Crustacea, Decapoda, Grapsidae )
摘要
過去大家所熟知的日本絨螯蟹 ( Eriocheir japonica ( de Haan, 1835 ) ) 在分類上屬十足目 ( Decapoda ) ，方蟹科 ( Grapsidae ) 。其分布北自庫頁島經朝鮮半島東岸、日本，南至中國大陸及台灣，包含諸多不連續的島嶼，且為台灣原生的絨螯蟹之一。現今在台灣主要分布於台中的濁水溪以北至宜蘭的白米溪，並於宜蘭的梗枋溪、新城溪與白米溪發現與台灣扁絨螯蟹 ( Platyeriocheir formosa ( Chan, Hung and Yu, 1995 ) ) 有共域的現象。本種在秋冬產卵的習性與台灣扁絨螯蟹於春夏之際產卵不同，除了具有相當高的經濟價值之外，在學術研究上更有重要的地位。 本研究利用 PCR 與定序等技術，以粒線體 DNA 細胞色素氧化酶 I ( Mitochondrial cytochrome oxidase I, COI ) 序列前段 555 bp作為分子標記 ( Molecular marker ) ，利用此分子標記探討台灣本島內日本絨螯蟹的遺傳多樣性與族群遺傳結構，總共分析了台灣與琉球沖繩地區 61 隻的日本絨螯蟹個體。結果在序列鹼基對比例方面，發現呈現 A – T rich 的現象，並加入從 GenBank 所獲得的四條序列，共得到 23 個基因型。由 DnaSP version 4.0 計算單倍基因多樣性指數 ( Haplotype diversity, h ) 與核苷酸多樣性指數 ( Nucleotide diversity, π ) 得知高的單倍體基因多樣性指數與低的核苷酸多樣性指數的結果，再利用 Tajima’s D 和 Fu and Li’s D 的中性檢定結果，顯示顯示族群有擴張的現象，因此，推測日本絨螯蟹族群曾經歷過瓶頸效應，而後快速擴張。以 Neighbor – joining 法進行親緣關係數的建構，顯示東亞地區分成日本、琉球沖繩、與台灣及中國大陸等三大群，其 bootstrap 值皆高於 90 。推測，真正的日本絨螯蟹應僅是產於日本本島的族群，而台灣及中國大陸的族群，實應歸屬於合浦絨螯蟹 ( E. hepuensis ) ，琉球沖繩地區的絨螯蟹則應為一新種，其學名暫定為 E. sp. nov. 。造成日本、琉球沖繩與台灣及中國大陸分成三群的原因，可能是受到 Kerama 與 Tokara 兩海槽的影響。根據 NJ Tree 分群的結果，建議將其分成三個演化有效單位 ( ESU ) 與管理單位 ( MU ) 進行保育管理。台灣島內的三個小地理區的族群呈現低遺傳分化與高基因交流的現象，推測，沿岸流可能是造成各族群交流的主要原因之一。
並列摘要
The Japanese mitten crab, Eriocheir japonica (de Haan, 1835), belonged to Decapoda, Grapsidae, is distributed in eastern Asia including Sakhalin, the eastern Korean Peninsula, Japan, China and Taiwan. In Taiwan, it is distributed in the northwest of Taiwan, from Juo-Shuei River in the central Taiwan to Bai-Mi River in Yilan County. This species and the Taiwanese mitten crab, Platyeriocheir formosa, are sympatric in Keng-Fang River, Shin-Cheng River and Bai-Mi River, which are located in Yilan. The reproductive behaviors are different between the two mitten crabs in Taiwan. The Japanese mitten crab migrated and reproduced in autumn and winter but the Taiwanese in spring and summer. Mitochondrial COI gene was used to be a molecular marker to reveal the population genetics of E. japonica in Taiwan. Sixty-one specimens were analyzed and a partial fragment of COI gene, whose size is 555 bps in length, was obtained. Twenty-three haplotypes were obtained including 3 classified from four sequences in GenBank. The high haplotype but low nucleotide diversity of the Japanese mitten and the results of Tajima’s D and Fu and Li’s D test were indicated that the populations of Japanese mitten crab have experienced bottleneck effect and population expansion event in the past. The NJ tree of the mitten crabs have shown that the Japanese mitten crabs are divided into three major groups with high bootstrap, which are group Japan, group Okinawa and group Taiwan and China. This division may result from the affections of Kerama and Tokara gap in western pacific. We hypothesize that there might be three species existed in Japanese mitten crabs. E. japonica could indicate the populations in Japan. The populations in Okinawa could be a new specie ( E. sp. nov. ) and the populations in Taiwan and China could be the members of E. hepuensis. In order to protect the populations of Japanese mitten crabs in Taiwan, three evolutionarily significant unit ( ESU ) and management unit ( MU ) should be proposed. The low genetic diversity and high frequent gene flow among the populations of Japanese mitten crabs in Taiwan could be influenced by the coastal current.