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標題: | 由族群遺傳結構探討白頭翁與烏頭翁之演化關係 The evolutionary relationship of Chinese Bulbul (Pycnonotus sinensis) and Taiwan Bulbul (P. taivanus) revealed by their population genetic structure |
作者: | Yu-Teng Hsu 許譽騰 |
出版年 : | 1999 |
學位: | 碩士 |
摘要: | 白頭翁(Chinese Bulbul, Pycnonotus sinensis)和烏頭翁(Taiwan Bulbul, P. taivanus)之間的地理隔離和自然雜交現像是研究種化過程的好題材,我們利用聚合?連鎖反應(PCR)和自動DNA定序(automated DNA Sequencing)技術,以具有快速演化特性的粒線體DNA控制區序列當作遺傳標記,研究白頭翁4個亞種(大陸亞種P. s. sinensis;海南亞種P. s. hainanus;琉球亞種P. s. shirogashira;台灣亞種P. s. formosae)與烏頭翁的族群遺傳結構和演化親緣關係。研究樣本來自18個採樣點、258隻個體(包括52隻雜交帶個體),利用長度1110bp(包含長度1081bp的粒線體控制區和29bp的t-RNAPro)的粒線體DNA序列,以NJ法重建27隻白頭翁四個亞種與烏頭翁特有種的演化親緣關係樹,所得之關係樹無法明顯區分出白頭翁與烏頭翁的演化親緣關係。以粒線體控制區5'端高變異的536bp序列分析白頭翁、烏頭翁與雜交區個體的族群遺傳結構時,共發現123個基因型,族群內的遺傳多樣性指數(h和π)顯示,單倍基因型多樣性指數(h)在每個族群都很高,平均值是0.925(從0.725到1之間),其中h值較小的族群都是來自於島嶼(金門,h=0.769;琉球,h=0.725);核?酸多樣性指數(π)在所有族群都不高,平均值是0.00906(從0.00538到0.01208)。Tajima's D和Fu and Li's D test顯示D值都沒有顯著偏離0,表示我們所選用的這段536 bp的粒線體控制區DNA序列在族群中的演化為中性的。所得族群間遺傳分化程度的指標值(dA、NST和AMOVA階層分析的結果)也顯示白頭翁與烏頭翁之間沒有明顯的族群遺傳結構和遺傳分化現象。依據基因交流量Nm值以及每個族群之間(除了廣州族群和採樣數小於3的族群以外)皆有共同的基因型,我們判斷白頭翁與烏頭翁之間的基因交流十分頻繁。島嶼間的粒線體DNA基因型關聯顯示,現今琉球群島上的白頭翁P. s. shirogashira族群極有可能是從台灣南部播遷過去,而且在外形上琉球白頭翁與台灣白頭翁族群十分相近。根據前人的研究和本實驗的結果顯示白頭翁與烏頭翁在生態、行為和遺傳上的差異並不明顯,也沒有生殖隔離的現象,故種間分化程度並不大,可能是在分化的初期,就因生態環境改變導致地理隔離消失而恢復基因交流。 The geographical isolation and natural hybridization between the Chinese Bulbul (Pycnonotus sinensis) and Taiwan Bulbul (P. taivanus) are criteria for a good example for studying the avian speciation process. We chose the rapidly evolving mitochondrial DNA (mtDNA) control-region (CR) sequences as genetic marker and used PCR and automated DNA Sequencing techniques to analyze the population genetic structure and phylogenetic relationship between 4 subspecies of Chinese Bulbul and Taiwan Bulbul. The 1110 bp mtDNA (including 1081 bp CR and 29 bp t-RNAPro) neighbor-joining tree for 27 individuals representing 4 subspecies of Chinese Bulbul and Taiwan Bulbul does not reveal any strict phylogenetic relationship between them. And a total of 123 haplotypes were detected in the 536 bp hypervariable segment of the CR of mtDNA for 258 individuals from 18 localities. The genetic diversity index (h and π) shows that the haplotype diversity (h) in every population is high, averaging 0.925 (range from 0.725 to 1); but the nucleotide diversity (π) is low, averaging 0.00906 (range from 0.00538 to 0.01208). Also, the neutrality test (Tajima's D & Fu and Li's D test) suggests that Chinese Bulbul and Taiwan Bulbul's mtDNA is evolving in a selectively neutral manner. Furthermore, the population differentiation index, including dA, NST and AMOVA, shows that there is no population genetic structure and only little genetic differentiation between Chinese Bulbul and Taiwan Bulbul. From the results of the gene flow (Nm) and identical haplotypes among populations, we infer that gene flow is the most plausible cause for the lack of little mtDNA differentiation between Chinese Bulbul and Taiwan Bulbul. Additionally, the haplotype relationship network shows that P. s. shirogashira on the Okinawa Island probably originated from the southern part of Taiwan and has close relationship with P. s. formosae morphologically. In conclusion, combined results of both our study and previous studies showed that no reproductive isolation and no apparent differences exist between them in ecology, behavior, and genetics. We propose that these two species were in the early stage of speciation but the geographic isolation disappeared because of recent ecological and environmental changes. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75054 |
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顯示於系所單位: | 動物學研究所 |
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