Abstract
The southern and tropical southeastern regions of the Yunnan Province in southwestern China have similar monsoonal climates and lowland tropical rain forest vegetations. The floras of both regions are dominated by tropical floristic elements (78.3% in southern Yunnan and 68.83% in southeastern Yunnan), and both belong to the Indo-Malaysian flora at the northern margin of tropical Asia. However, some temperate East Asian characteristic families are well represented in the flora of tropical southeastern Yunnan, while families characteristic of tropical Asia are well represented in the flora of southern Yunnan. Additionally, there are 14 mainly east Asian families in tropical southeastern Yunnan that are not found in southern Yunnan. Although the two regions share 80% of their genera, 237 genera are restricted to southern Yunnan, and 349 genera to tropical southeastern Yunnan. Furthermore, 57 genera with an East Asian distribution, 53 genera with a North temperate distribution, 22 genera endemic to China, and 17 genera with an East Asia and North America disjunct distribution are found only in tropical southeastern Yunnan. The flora of tropical southeastern Yunnan is more closely related to Eastern Asian flora, while the flora of southern Yunnan is more closely related to Indo-Malaysian flora. The divergence of the flora is well supported by the geological history of the region; the flora of tropical southeastern Yunnan was mainly derived from the South China Geoblock, while the southern Yunnan flora derived from the Shan-Thai Geoblock.
Highlights
Yunnan, in southwestern China, is a region of exceptional interest to biologists because it is situated in a transitional zone between tropical south-east Asia and temperate east Asia [1,2], and because it was at a sutural zone between Gondwana and Laurasia [3,4,5]
Geographical elements at the generic level reveal that the floras of southern and tropical southeastern Yunnan are dominated by tropical elements, of which, the tropical Asian elements make up the highest proportion
Both floras were categorized as the tropical Asian flora in the floristic regionalization of the world [1,2], i.e. they belong to the Malaysia subkingdom of the Paleotropical kingdom
Summary
In southwestern China, is a region of exceptional interest to biologists because it is situated in a transitional zone between tropical south-east Asia and temperate east Asia [1,2], and because it was at a sutural zone between Gondwana and Laurasia [3,4,5]. Little was known about the tropical flora and vegetation of southwestern China until the late 1950s because of poor access. It was suggested that tropical rain forests existed in southwestern China, but these were considered different from those in Indo-Malaysia [7,8]. Further biogeographical and ecological studies on the vegetation and flora of tropical southwestern China revealed that it is comprised of Indo-. The tropical flora in southern Yunnan differs from that of southeastern Yunnan, the two regions have a similar climate and the same tropical rain forest at lowlands as those of southeastern Asia. The flora of the tropical region of southeastern Yunnan has a relatively high proportion of temperate east Asian characteristic families, such as Magnoliaceae, Cornaceae, Smilacaceae, Theaceae, Styracaceae, Symplocaceae, Aquifoliaceae, Caprifoliaceae and Celastraceae, while in southern Yunnan, tropical Asian characteristic families, such as Meliaceae, Annonaceae, Menispermaceae, Zingiberaceae, Apocynaceae, Asclepiadaceae, are well represented. Based on comparisons of floristic composition and geological history between southern and tropical southeastern Yunnan, I will discuss the biogeographical divergence between these regions
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