The distribution of tropical rainforest is very limited today in China. alaeovegetation reconstruction based on palynology indicates that the tropical rainforest was almost or completely absent from mainland China during the Late Glacial Maximum, but little is known about the occurrence of rainforest in China during the early Neogene. The occurrence of Dipterocarpaceae from the middle Miocene of China raises the question of the route of exchange between Chinese and Indian palaeofloras. Based on southwestern Chinese palaeofloras, no floristic link could be made between Miocene vegetation of China and India.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and Nanjing Institute of Geology and Palaeontology uncovered fossils from Fotan flora. Their investigation will help to clarify the biogeographic link between this flora and the Indian palaeo floras. They described six new species from the Fotan flora, discussed their affinities, and elucidated whether they are consistent with the presence of a tropical forest. In addition, they discussed the biogeographical implications.
The fossils were identified through detailed comparison with leaves of living plants. Six new species belonging to six different families are described: Artocarpus basirotundatus sp. nov. (Moraceae), Bauhinia fotana sp. nov. (Leguminosae), Boehmeria fujianensis sp. nov. (Urticaceae),Calophyllum striatum sp. nov. (Calophyllaceae), Flacourtia serrulata sp. nov. (Salicaceae), and Macaranga stellata sp. nov. (Euphorbiaceae).
The presence of a tropical forest in South Fujian during the middle Miocene previously suggested by the Dipterocarpaceae fruits is corroborated by these six new elements. The Fotan palaeoflora demonstrates that the climate at low latitudes also changed: the limit between tropical and subtropical belts moved a few degrees northwards, at least north to South Fujian.
The Fotan flora is unique amongst Chinese Neogene palaeofloras. Five of the genera reported in their study, ie. Artocarpus, Boehmeria, Macaranga, Flacourtia, and Calophyllum, were not known previously from the Chinese fossil records. Sharing several components, some of them presumably dominant components, the Fotan palaeoflora and the Indian palaeofloras demonstrate that vegetation exchanges between the Indian Gondwanan land and Laurasia were strong at that time.
Based on the Fotan palaeoflora, they suggest that, under the out-of-India hypothesis (i.e the uniqueness of the Indian flora was diluted by the floristic interchange with Asia after the collision started), this dilution was already important at the time of the middle Miocene. They suggested that during the Mid-Miocene Climatic Optimum, the tropical rainforest could have moved northwards up to South Fujian. Their results suggested that there could have been strong floristic links between India, South-East Asia and South China during the middle Miocene, with a continuous tropical forest zone.
Author Contact:
ZHOU Zhekun, Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
Tel: 86 691 8716932
Fax: 86 691 8715070
E-mail: zhouzk@xtbg.ac.cn
