牛樟、冇樟及樟樹之族群遺傳變異及相關種屬之親緣關係研究

Abstract

牛樟、冇樟與樟樹為樟科樟屬內形態相近的相關種，三者在空間分布上，廣狹不同。本研究用ISSR分子標誌檢測三者之族群遺傳結構，並以NTSYS進行群團分析及主成分分析並以POPGENE及AMOVA軟體分析其族群結構及變方。 樟樹為廣泛分布種，樟樹台灣地區之樟樹與大陸地區之樟樹大致形成2個群團連結，再與恆春半島地區之種源聯結，並以日本琉球地區石垣島之樟樹作為對照。變異數分析（AMOVA）。結果顯示大陸產、台灣產與日本石垣島之樟樹間變方成分為45.40％，而區域內族群間之變方成分為26.64 ％，族群內個體間的變方成分為27.96％。樟樹種內的遺傳歧異度為0.2564，就族群分化係數（Gst）來看，為0.4881，基因流轉（Nm）的數值為0.5244，基因流的數值則低於1，顯見兩岸之樟樹族群間存有交流障礙。 冇樟為區域性分布種，本研究利用台灣地區之冇樟及大陸廣東地區之冇樟為材料進行分析，結果在群團分析及主成分分析上都可明顯分成2個群聚：第1群是台灣冇樟，第2群為大陸廣東地區的冇樟。在POPGENE之遺傳距離分析上廣東地區冇樟與台灣地區之冇樟相似性係數極低在0.5445至0.4316之間，兩區域間之相似性係數已低於種間的相似性係數之值。台灣地區之冇樟族群族群分化係數（Gst）為0.3021，在基因流轉（Nm）的數值為1.1548，基因流的數值高於1，顯見台灣之冇樟樹族群間不存有交流障礙。將大陸種源冇樟樹和台灣種源的冇樟當作2區域進行變異數分析（AMOVA），依據區域間、區域內族群間及族群內個體間等分析三個等級之變方成分。結果大陸產之冇樟、台灣產冇樟間變方成分為56.37%，而區域內族群間之變方成分為13.19 %，族群內個體間的變方成分為30.44%。 牛樟為台灣特有種，在NTSYS軟體的群團分析及主成分分析上都可明顯分成2個群聚：1群是台灣牛樟，另1群大陸廣東地區的冇樟。在台灣牛樟族群無法區分各個族群。但台灣地區之牛樟族群的相似性係數與地理距離分布並無正相關。族群分化係數（Gst）為0.3490，基因流轉（Nm）的數值上為0.9328，基因流的數值則低於1，顯示牛樟族群間可能因近年來人為開採而導致族群減少，各族群間已有交流障礙產生。 在POPGENE分析牛樟、冇樟和樟樹親緣關係，以牛樟與樟樹兩者之遺傳距離僅為0.0997來推論，印證藤田安二（1952）以精油成分分析，認為牛樟由樟樹演變而來的結果相符。cpDNA所建立的樹狀圖及距離矩陣都顯示出，本研究所使用的台灣地區之冇樟與大陸廣東地區之冇樟有著極大的差異存在。 台灣地區之樟屬植物以葉綠體DNA中之2片段（PetD-PetB、TrnS-TrnT）定序結果顯示，約略可將樟屬區分成樟組及肉桂組，其分子證據與傳統之分類處理大致符合。再以葉綠體DNA中之3個片段（PetD-PetB、TrnV-TrnM、TrnS-TrnT）定序結果以及Kimura’s 2-parameter distance遺傳距離顯示，菲律賓樟（Cinnamomum philippinense）應改隸為楨楠屬，學名應為菲律賓楠（Machilus philippinensis Merr.）。而酪梨屬和楨楠屬之遺傳距離較近。且在NJ法及MP法的分枝圖都將酪梨屬與靠近，但在形態上兩屬仍有很大的差異點，楨楠屬是不是應併在酪梨屬之下仍有待商榷。 未來在擬定保育方針與保育措施時，結果顯示三者的方式皆不同。牛樟為固有種，主要變異存在於族群內，高達90%以上，而分布範圍稍大的冇樟應屬區域性分布，其主要變異成份在族群內及族群間各占約二分之ㄧ，也就是一半的變異存在族群內，另一半存在族群間。而樟樹為廣泛分布種，則其大多的變異是存在於族群間，約為族群內變異的2倍之多。樟樹應以保留多數的族群和族群內少數的單株；而冇樟則是族群數量及族群內也要有相當的數量，但是牛樟則應該保存少數族群內大量的單株。

Cinnanamomum kanehirae, C. micranthum and C. comphora are morphologically related species. The distribution patterns of the three are different from each other, i.e. C. kanehiraeis an endemic species and confined only in Taiwan Island, where as C. micranthum regional which reaches its areas not only to Taiwan but also to southern China. C. camphora has the most widely distribution areas of the three which is native to Japan, Korea and Indochina peninsula. The study used ISSR, cpDNA techniques to analyzed genetic variation and phylogenetic relationship of the three species as well as the other species in the family to obtain better understanding of their variation pattern and taxonomic position. The populations of C. camphora from Taiwan and China had formed two different regins according to NTSYS cluster and PCO analyses. Variation component of the species among the areas of Taiwan, China and Okinawa was 45.4% While among population within region 26.64% and among individual within populations 27.96%. POPGENE analysis showed that genetic diversity of the species was 0.2564, Gst 0.4881, Nm0.5244, indicating that gene flow barrier existed in the populations. Two distinct groups of the C. micranthum populations were identified based on the analyses of both cluster and PCO, i.e. Taiwan group and China group. Similarity indices between the two ranged from 0.4316 to 0.5445 suggesting two groups were different from each other. The Chinese populations had long been misidentified as C. micranthum, and need to use new epithet. Gst and Nm values of the Taiwanese populations were 0.3021, 1.1548, respectively, indicating gene exchanged among populations was freely and without any difficulty. Variaties components of the species was as follows: between areas （Taiwan and China）56.3%, among populations within area 13.19% and among individuals within population 30.44%. On the contrasty, there was as differentiaties among the populations of the endemic Cinnamomum kanehirae, i.e. no dististinct groups could be identified according to NTSYS cluster and PCO analyses. Farthermore, the SI differentes among the populations of the species did not related with their geographical distances. Nm value of the species was 0.9328(<1), suggesting gene exchange had become diffcult partly because of human disturbance. The results of POPGENE analysis revealed that genetic distance between C. kanehirae and C camphora was only 0.0997, indicating high relationship between the two. The data highly supported the proposed by Fujita (1952) that C. kanehirae was derived from C. camphora based on essential oil study. On the other hand, cpDNA analysis showed that the so called ”C. micranthum” of the Guan dong origin was quite different from the species of Taiwan with the same epiphyte, suggesting the mainland “species ” was the other species rather than C. micranthum. Non-coding segment cpDNA PetD-petB, TrnV-TrnM and TrnS-TrnT and Kimura’s 2-parameter distance were used to study the phonology of Cinnamomum philippinese and the relationship between genera Persea and Machilus. The dendrology of both NJ and MP methods revealed that Cinnamomum philippinse was closer to Machilus than to Cinnamomum genetically. Therefore the species was suggested to put under the genus Machilus. The result of the same cpDNA study also indicated that Machilus and Persea were different. Based on the AMOVA analysis, variation patterns of C. kanehirae, C. micranthum and C. camphora were quite different. Variation of C. kanehirae mainly exists in individuals within population, estimated more than 90%, whereas that of C. micranthum almost equally in terms of within and among populations. The variation among the populations of C. camphora was almost 2 times of the individuals within population. Conservation strategy for these three species is accordingly suggested to adopt different ways.