黃裳鳳蝶之保育生物學研究

Abstract

全世界的黃裳鳳蝶Troides aeacus formosanus (Rothschild)，目前分為五亞種，T. a. aeacus Felder, T. a.szechwanus Okano & Okano, T. a. malaiianus Furhsorfer, T. a.insularis Ney, and T. a. formosanus (Rothschild)，分佈西起北印度、尼泊爾、不丹、錫金、華西、華南各省及中南半島、海南、香港及臺灣。臺灣黃裳鳳蝶Troides aeacus formosanus (Rothschild)為特有亞種，也臺灣本島唯一分布的鳥翼蝶，主要分布於臺灣東南部平地至500公尺低地山區，其體型屬大型蝶種及後翅具有美麗的金黃色斑紋，野外數量因食草與棲地破壞而減少，並且具獵捕的壓力，而於1989年被臺灣野生動物保育法列為保育等級第2級之珍貴稀有種的蝴蝶；黃裳鳳蝶的幼蟲以馬兜鈴科(Aristolochiacea)的植物為其寄主植物，因本種蝴蝶列為保育類昆蟲故目前仍為禁止、採集飼養的物種，但在一些民間的蝴蝶園中，因其外型大且美麗，又是臺灣僅有分布的一種鳥翼蝶物種(birdwing butterfly)，雖已漸有繁殖成功之實，但多未對本種蝴蝶進行全面性之生物學基本研究及野外族群的調查；而在世界自然保育聯盟組織(IUCN)，對鳳蝶保育行動計畫(action plan)，曾提出二個進行的方向(approach)：分別為群聚導向(community-orientaled)及物種導向(species-orentated)，而第一種是將鳳蝶的保育整合成廣義的保育計畫，因鳳蝶本身就可當作其他種的保育基礎；而第二種則可延伸到物種，以物種本身做為保育焦點，而相對於群聚導向，物種導向主要的目的是鼓勵與發展對這些物種的復育計畫，因此本研究完成了黃裳鳳蝶之族群生態、分布、棲地、生活史等保育生物學資料之建立，並對人工繁殖與蝴蝶農場對本種是否有潛在的風險評估等研究。 結果顯示，黃裳鳳蝶現今在台灣各縣市皆有分布，但仍以屏東縣的數量最多，其次為高雄、台東與花蓮縣。而在垂直分布上，仍以海拔0-500公尺的數量最多，目前分布最高的紀錄為2000公尺的梨山地區。在黃裳鳳蝶之生活史及相關生物學研究上，完整紀錄臺灣黃裳鳳蝶於各地的形態上並無差異，雌蝶體型大型雄蝶。卵期為7.93±072天(n =29)；幼蟲期1至5齡分別為4.46±0.79天(n =28)、5.52±1.45天(n =27)、5.33±1.41天(n =27)、6.19±1.49天(n =26)、9.80±1.36天(n =25)，蛹期30.21±1.42天(n =19)；結果顯示，完成一世代所須的時間約60.74±2.83天。另依各階段在不同溫度之所計算出的迴歸線:卵的發育起始溫度為攝氏 7.66度；幼蟲期在同溫度之所計算出的迴歸線：發育起始溫度為攝氏7.81度，蛹為攝氏12.71度。有效積溫在4個溫度下分別為，卵期145.42日度、136.87日度、137.51日度及143.62日度；幼蟲期為514.09日度、490.27日度、504.87日度及471.27日度；蛹期為325.10日度、412.92日度、326.55日度及362.78日度。黃裳鳳蝶應仍較適應熱帶型的氣候。在幼蟲期之食葉量測定上，黃裳鳳蝶各齡幼蟲的食葉量分別為5.35 ± 2.30 c㎡(n=10)、15.92 ± 4.14 c㎡(n =10)、122.43 ± 36.75 c㎡(n =10)、250.67 ± 57.48 c㎡(n =10)、1338.9 ± 148.93 c㎡(n =10)，幼蟲期總計須1733.30± 137.17 c㎡，五齡幼蟲是食量最大的時期，是第1齡的324倍，也較四齡幼蟲高出5.34倍。充量的葉片與植株，才足以供給黃裳鳳蝶幼蟲成長的需求。 另外，本研究由 CO I及 AFLP 二種的分子指紋技術檢測，皆顯示臺灣的黃裳鳳蝶各地族群間的變異不大，所以各族群間並没有明顯的遺傳結構，因此可視為一個大的族群，但黃裳鳳蝶本身遺傳多樣性並不高，僅只有4個基因型（haplotype），但就其族群分化的方向，南部的恆春半島應為母族群的分布地，故墾丁國家公園及滿州的族群將是未來保育的重點，因為其是臺灣其他族群維持遺傳多樣性根源，也是維繫本種在台灣能否永續經營的重要關鍵。而由臺灣亞種與中國亞種COI變異2-4個鹼基，可推測臺灣與中國的亞種，因更新世冰河期的影響，海平面降低之後，於12000-150000年前之間遷移至臺灣；而後分隔在中央山脈的兩邊，因此在CO I或AFLP的分析都有兩大群的演變結果，分化時間大約是60000年前。因近期人為捕捉釋放或飼養的關係，野外族群可能因人為因素而形成基因交流頻繁的情形，造成各地小族群均有兩型的黃裳鳳蝶分布。 由遺傳多樣性結果，除了未來應加強墾丁國家公園及滿州族群的保育外，在各地的族群中，擁有較稀有的基因型，如滿州及新竹地區的族群，也應加強復育此擁有基因型較稀有的族群。另外，除了國家公園及林區管理處應加強對本種的棲地保護外，也應進行對各地蝴蝶園經營者之進行教育宣導，加強經營者正確之族群管理及保育遺傳學概念，以免有將人工繁殖即為保育的錯誤觀念。

Troides aeacus is distributed throughout the eastern and southern Asia, which consists of five subspecies, including T. a. aeacus Felder, szechwanus Okano & Okano., malaiianus Furhsorfer, insularis Ney, and formosanus (Rothschild). Common name of T. a. formosanus (Rothschild, 1899) found in Taiwan is “small birdwing”, T. a. formosanus is an endemic subspecies restricted its distribution in Taiwan; and is protected by CITES; and is one of the five Troides aeacus subspecies. The wingspan of T. a. formosanus could reach 150 mm. It also is one of the two representative birdwing butterflies of Taiwan. The black forewings and golden hind wings of the small birdwing are decorated with black dots and grayish stripes, and there are red hair on the either side of its head. The small birdwing is fairly large in size, elegant and precious, so it is very popular to collectors, and has been severely threatened by commercial collection since 1950s. In 1974, the Entomological Supplier Association of Great Britain agreed not to trade the endemic Taiwan subspecies T. a. formosanus, and Council of Agriculture has listed it on Appendix II of Wildlife Conservation Law in Taiwan in 1989. In addition to the captured threat, the population decline is also associated with habitat loss of the host plant of Aristolochia spp., which are climbing vines. It is known that large numbers of plants are required to sustain a healthy small birdwing population. In this study, the life cycle and the development time of the T. a. formosanus under different temperatures were tested. The results showed that the egg stage took 7.93±072 days (n=29), the larvae stage from 1st to 5th took 4.46±0.79 days (n =28), 5.52±1.45 days (n=27), 5.33±1.41 days (n=27), 6.19±1.49 days (n=26), 9.80±1.36 days (n=28) respectively. The pupae stage was 30.21±1.42 days (n =19). I also found that as the rearing temperature increased, the development rate increased at the same time. The lower developmental threshold temperatures for the development of eggs, larvae, pupae, were estimated to be 7.66, 7.81, 12.71℃, respectively. The 4 temperature of accumulative effective temperatures of eggs were 145.42, 136.87, 137.51 and 143.62 degree-days；the larvae were 514.09,490.27, 504.87 and 471.27 degree-days；and pupae were 325.10, 412.92, 326.55 and 362.78 degree-days。The area of leaf consumption from 1st to 5th larvae stage were 5.35 ± 2.30 c㎡(n =10)、15.92 ± 4.14 c㎡(n =10)、122.43 ± 36.75 c㎡(n =10)、250.67 ± 57.48 c㎡(n =10)、1338.9 ± 148.93 c㎡(n =10), respectively. The results provide information for the conservation management of the T. a. formosanus population. Troides aeacus formosanus is one of the five T. aeacus subspecies regions and endemic to Taiwan. In this study, partial DNA sequences of cytochrome oxidase I (CO I) and amplified fragment length of polymorphism (AFLP) markers were analyzed to delineate the differentiation and possible dispersal history of this birdwing butterfly. Phylogenetic relationship analyses have shown that T. a. formosanus could be divided into lineages I and II with limited CO I variations; and AFLP patterns have also shown two divergent clusters A and B. In populations collected from southern Taiwan, there was a significant relationship between lineage II and cluster B. Parsimonious network of CO I indicated haplotype HI, the nearest to the other subspecies, should be the basal in T. a. formosanus. Both CO I sequences and AFLP patterns indicated that haplotype diversity was high in all populations, whereas low levels of genetic differentiation were found among populations. Analysis of molecular variance suggested that most of the total variance was due to differences within populations. These results together with the divergent estimation and the specific geological topology in southern Taiwan indicated that T. a. formosanus might have moved in during recent glaciations (about 150,000 years ago) and become adapted to the tropical environments. The observed differentiation of T. a. formosanus might have resulted from the geographic barriers of the Central Range in the island of Taiwan. Moreover, genetic exchanges caused by transportation and translocation of individuals among butterfly farms or gardens in the past two decades have possibly led to the less diversification among current populations of T. a. formosanus.