Molecular phylogeny of Bemisia tabaci (Hemiptera: Aleyrodidae) complex

煙草粉蝨 (Bemisia tabaci) 為多食性農業害蟲，廣泛分佈於熱帶與亞熱帶地區，種內具有形態無法區分，但有其他生物特徵可供區分的族群，目前利用多種技術及方法鑑定出至少 30 型生物小種 (biotype)，包括病徵測試、同功異構酶和 DNA 分子標記等。煙草粉蝨被認為是一種群，包含許多生物小種以及被命名的兩個種：煙草粉蝨 (B. tabaci) 及銀葉粉蝨 (B. argentifolii)。本研究利用分子標記來進行煙草粉蝨複合群分子系統發生學之研究並分為五大主題。一、利用粒線體 COI 進行系統發生分析，結果顯示亞洲地區有兩個本土的生物小種重疊分佈，分別為Nauru與AN生物小種，並指出 Nauru 生物小種可能是亞洲起源，而 AN 生物小種可能是亞洲或澳洲起源。二、粒線體 COI 系統發生分析亦指出 B 和 Q 生物小種存在於西北太平洋地區為多次近期入侵事件，並與來自地中海的景觀植物貿易相關。三、煙草粉蝨生物小種同物異名現象也是一個重要的議題。所有的煙草粉蝨生物小種樣本經粒線體 COI 系統發生分析後被分為 9 個遺傳群，分別為亞澳群、亞洲群、義大利群、地中海-北非群、地中海-中亞-非洲群、東南非洲群、新世界群、撒哈拉沙漠以南非洲群及烏干達群，並顯示這些遺傳群的分佈與地理區相關。另外，煙草粉蝨起源地一直是爭論的議題，因此本研究亦進行煙草粉蝨複合群起源與分化之研究，驗證非洲起源假說與南亞起源假說，經粒線體 COI 系統發生分析，結果顯示非洲樣本位於系統樹基部並支持非洲起源假說。四、本研究亦檢驗煙草粉蝨隱蔽種群假說，選擇與煙草粉蝨關係接近的種與屬來進行系統發生分析，結合粒線體 COI 與 16S 之分析顯示煙草粉蝨複合群並非單系群，因此支持煙草粉蝨為隱蔽種群。煙草粉蝨遺傳群間亦觀察到生殖隔離與顯著不同的生物特徵並更支持煙草粉蝨為隱蔽種群。五、煙草粉蝨亞洲群與亞澳群共存於亞洲是令人困惑的，因此提出同域分化後輻射擴散假說與異域分化後的二次接觸假說。此外，本研究利用微衛星 DNA 與粒線體 COI 進行族群遺傳結構與親緣地理學研究來驗證假說，結果顯示此兩本土遺傳群同域分佈是屬於異域分化後的二次接觸，並指出亞洲群與亞澳群皆起源於亞洲。然而，煙草粉蝨仍有許多有趣的議題尚未解決，仍須未來進一步的研究。Bemisia tabaci (Gennadius) is an important agricultural pest that is polyphagous and widely distributed throughout tropical and subtropical areas of the world. Morphologically indistinguishable populations with different biological traits exist within B. tabaci. More than 30 biotypes of B. tabaci have been identified by multiple techniques that include specific phytotoxic reactions, isozymes, and DNA markers. Bemisia tabaci was proposed to be a species complex, with many biotypes and two described extant cryptic species, B. tabaci and B. argentifolii. In this study, molecular markers were used to study the molecular phylogeny of the B. tabaci complex. Phylogenetic analyses of mitochondrial cytochrome oxidase I (COI) gene sequences revealed two indigenous biotypes with overlapping distributions in East Asia: the Nauru and AN biotypes. The results also showed that the Nauru biotype is of Asian origin, and the AN biotype could be of Asian or Australian origin. In addition, phylogenetic and population genetic analyses indicated that biotypes B and Q occur in the Western North Pacific region due to multiple recent invasions. The invasive events were related to the ornamental plant trade from the Mediterranean region. Furthermore, synonymy of biotypes is also an important question which needs to be studied. All biotypes of B. tabaci were used to reconstruct a phylogenetic tree, and results indicated the existence of nine genetic groups: Asia-Australia, Asia, Italy, Mediterranean/North-Africa, Mediterranean/Asia Minor/Africa, Southeast Africa, New World, Sub-Saharan Africa, and Uganda. The distributions of genetic groups were related to the geographic region. The origin and divergence of B. tabaci were also discussed in this study. Hypotheses of originating in Africa and in South Asia are proposed and tested. Phylogenetic analyses revealed that samples from Africa formed the basal clade, which supports the out-of-Africa hypothesis. On the other hand, the hypothesis of a cryptic species complex of B. tabaci was also tested in this study. Whiteflies close to B. tabaci were also selected to reconstruct a phylogenetic tree and discuss the issue of a B. tabaci species complex. Phylogenetic analyses of COI and 16S ribosomal DNA revealed that B. tabaci is not a monophyly and support it being a species complex. Reproductive isolation and significantly different biological characters were also observed among genetic groups and provide information to suggest the existence of a B. tabaci species complex. Moreover, Asia and Asia-Australia genetic groups coexisting in Asia is also confusing. Hypotheses of sympatric divergence with radiating expansion and allopatric divergence with secondary contact were proposed. Microsatellite and mitochondrial markers were used to study the population structure and phylogeography of indigenous genetic groups of B. tabaci in Asia. Results revealed that the sympatric distribution of two indigenous genetic groups in Asia represents allopatric divergence with secondary contact. Furthermore, the Asia and Asia-Australia genetic groups both originated in Asia. However, there are still many interesting questions which need to be studied in B. tabaci in the future.口試委員會審定書.......………………………………………………………………….i謝…...…………………………………………………………………………………ii文摘要…...…………………………………………………………………………...iiibstract…………………………………………………………………………………..vist of Tables……………………………………………………………………………xiist of Figures…………………………………………………………………………xiiihapter 1 eneral Introduction………………………………………………………………..1hapter 2aterials and Methods……………………………………………………………5hapter 3nalysis of biotypes of Bemisia tabaci and distribution in Eastern Asia based on mitochondrial DNA marker.1 Introduction…………………………………………………………………14.2 Results………………………………...……………………………………15.3 Discussion………………………………………………………………..…23hapter 4vidence from molecular markers and population genetic analyses suggest recent invasions of the Western North Pacific region by biotypes B and Q of Bemisia tabaci (Gennadius).1 Introduction…………………………………………………………………28.2 Results…………………………………………………………...…………29.3 Discussion……………..…………………………………………..………41hapter 5he origin and divergence of Bemisia tabaci complex.1 Introduction…………..……………………………………………………47.2 Results………………………………………………………………………49.3 Discussion……………………………………………………………………56hapter 6esting the hypothesis of a cryptic species complex for Bemisia tabaci using the molecular phylogeny of whiteflies.1 Introduction…………………………………………………………………65.2 Results………………………………………………………………………66.3 Discussion……………………………………………………………………76hapter 7nferring dispersal patterns from the sympatric distribution of two different indigenous genetic groups of Bemisia tabaci in Asia by mitochondrial and microsatellite markers.1 Introduction…………………………………………………………………83.2 Results……………………………………………………………………...…85.3 Discussion…………………………………………………………………103hapter 8onclusions……………………………………………………………………112eferences…………….………………………………………………………………116ppendicesublication 1...………………...…………………………………………………135ublication 2..……………………………………………………………………14