臺灣植物相之歷史生物地理學

歷史生物地理學主要研究生物的起源，傳播路線及分類群演化史中的多樣性變化。本文旨在總結到目前為止臺灣植物相有關此方面研究之成果，並測試前人提出來的觀點，大致依下例子題探討:1.臺灣之植物化石資料及臺灣島之誕生、2.物種經由那一條路線進入臺灣、3.臺灣植物相之來源區域、4.臺灣植物相中之中國－日本成份與中國喜瑪拉雅山成份分析、5.最早進入臺灣之植物是否分布在中海拔、6.物種入侵臺灣本、經琉球入臺灣。目前已知，入侵的溫帶植物大致於臺灣北部登陸，並慢慢往南擴散。臺灣最早入侵的植物則是存留在中海拔地區，而非隔離較大的高海拔地區。對溫帶植物而言，地形複雜之臺灣，於冰河期時從南到北都是避難所。但南北的氣候差異及複雜的地形，造成近萬年來各地區的族群只分布於局限的地區，無法擴散到全島。因此臺灣植物分區可細分成九區，以作為將來臺灣族群間散播的討論基礎。此九區可對應於臺灣之氣候分區。後的傳播方向、7.臺灣於冰河期之避難所、8.依植物現生分布樣式臺灣可分成幾個地理分區。結果顯示，臺灣之大型植物化石最早上溯到早中新世(23～16百萬年前)，不過其地層屬海相沉積，可能非臺灣自生;孢粉化石則上溯到漸新世(34～24百萬年前)，不過亦無法證明為臺灣自生，因此無法說明臺灣島何時有陸地存在。地質上臺灣島誕生時間的看法仍不一致，廣義來說大致是一千萬到五百萬年前誕生。臺灣現生植物相之來源是多源的，熱帶植物成份主要來自菲律賓，亞熱帶成份來自中南半島及中國大陸極南方，溫帶成份則來自日本，中國大陸的中國－日本植物亞區，中國一喜瑪拉雅山植物亞區。熱帶植物成份是由菲律賓呂宋經由巴丹、蘭嶼、綠島等到臺灣南部。亞熱帶成份則是由中南半島經廣西、廣東、海南島藉由陸橋進入臺灣南部。溫帶植物成份或由西部從喜瑪拉雅山東麓，經雲貴高原、南嶺入福建，藉由臺灣海峽形成之陸橋進入臺灣;或北由華東北、華東入福建，藉由東海或臺灣海峽形成之路橋進入臺灣;或北由日本、經琉球入臺灣。目前已知，入侵的溫帶植物大致於臺灣北部登陸，並慢慢往南擴散。臺灣最早入侵的植物則是存留在中海拔地區，而非隔離較大的高海拔地區。對溫帶植物而言，地形複雜之臺灣，於冰河期時從南到北都是避難所。但南北的氣候差異及複雜的地形，造成近萬年來各地區的族群只分布於局限的地區，無法擴散到全島。因此臺灣植物分區可細分成九區，以作為將來臺灣族群間散播的討論基礎。此九區可對應於臺灣之氣候分區。

關鍵字

臺灣；植物相；歷史生物地理學；傳播路線；避難所；植物區系；地理分區

並列摘要

Historical biogeography is a study on the origin, migration and diversification of a taxon. This paper is aimed to summarize the studies on this issue focusing on the flora of Taiwan, and tests some ideas proposed by earlier researchers. It was arranged according to the following subjects. 1. The plant fossils discovered in Taiwan and the origin of Taiwan island; 2. Migration routes for the plant species invading Taiwan ; 3. Where were source plant species that invaded Taiwan? 4. Distinction of Sino-Himalayan and Sino-Japanese elements in Taiwan. 5. Is it true that the earliest plants invaded Taiwan inhabiting middle elevation? 6. Migratory direction of plant species in Taiwan. 7. Refuges in Taiwan during glaciations 8. How many subdivisions can be recognized based on plant species distribution. Some conclusions may be drawn as follows. The timing of the origin of Taiwan is still debating based on geological data while the plant fossils discovered in Taiwan can not determined when Taiwan emerged from the sea because the megafossils are from sea-phase sediments and the microfossils are hard to prove that they are autochthonous. Broadly speaking, Taiwan may have originated during 10-5 million years ago. For the present flora of Taiwan, there are many source areas from which plant species invade Taiwan. The Philippines provided the tropical elements that invaded southern part of Taiwan through migration route of Luzon, Patan island, Lanyu and Green island, while IndoChina, southern tip of mainland China and Hainan might provide subtropical elements that also invaded southern Taiwan through land bridges formed by the South Sea during the glaciations. Jap an, Sino-Japanese region and Sino Himalayan region provided temperate elements to the flora of Taiwan. The species from Japan might migrate through the Ryukyu s and invaded northern Taiwan . The species from north-eastern and eastern China might migrate to south-eastern China and invaded northern and western Taiwan through land bridges formed by the East Sea and the Taiwan Strait during glaciations. The species from south-western China might migrate through Yunnan-Kueichou Plateau, via Nan-ling and went into Fuchien, from which they invaded western Taiwan via land bridges formed by the Taiwan Strait during the glaciations. So far as the data have shown , the temperate specie s invaded northern Taiwan and then migrated southwardly. The earliest colonizers in Taiwan inhabited the middle elevation rather than high elevation, although the later is more isolated. For temperate species, there were multiple refuges during the glaciations in Taiwan. However, the dispersal of species was restricted after the retreat of the last glaciation because barriers might have formed due to the complexity of topography of the island and difference in climate from the north to the south of Taiwan. Therefore nine subdivisions, which are corresponding to climatic zones recognized by earlier researcher, were distinguished based on the phylogeographical studies of plants. These nine subdivisions may serve as areas for future discussion on migratory topics in Taiwan.