Composition, Endemism and Phytogeographical Affinities of the Taiwan Flora

The Taiwan vascular flora is exceptionally interesting not only because it is rich and diversified, but because it is of great phytogeographic significance owing to its geographic location. The flora of Taiwan, including naturalized plants, comprises 233 families and 1389 genera with 4216 species. In terms of major growth forms, there are 588 trees, 426 shrubs, 249 lianas, 177 vines, and 2776 herbs or ferns. Approximately 234 species are exotics typically associated with pastures, road clearings and other human disturbances. An extremely large percentage of these naturalized plants are of tropical New World origin. Among the native flora, the Orchidaceae (331 species), Gramineae (249), Compositae (194), Leguminosae (176), Cyperaceae (174), Rosaceae (105), Rubiaceae (93) and Euphorbiaceae (76) rank highest in numbers of species. Clearly, the greatest part of Taiwan's floristics richness comes from a wealth of species in primarily lowland (0–600 m asl.) taxa. A total of 2571 species were recorded in the lowlands, whereas only about 251 species occur between 3100-3950 m. Endemic genera are extremely scarce in Taiwan, with only four, namely Sinopanax (Araliaceae), Hayatella (Rubiaceae), Kudoacanthus (Acanthaceae), and Haraella (Orchidaceae). In contrast to the low percentage of generic endemism, there is a remarkably higher specific endemism. About 1041 species (26.1% of indigenous plants) are known only from Taiwan. A detailed examination of these species shows that there is a distinct trend of increasing endemism with increasing altitude (r² = 0.99). A survey of indigenous non-endemic species on the basis of their geographical distribution outside Taiwan shows that they can be classified into 6 major categories: 1. pantropical and palaeotropical species (1029 species); 2. species distributed in eastern Asia, from Himalayas through southern & eastern China to Taiwan, with some extending to the Ryukyus and Japan (1075 species); 3. widespread species extending from tropical Asia to eastern Asia (232 species); 4. species distributed in Japan and the Ryukyus (189 species); 5. species distributed in temperate and subboreal regions (221 species); and 6. cosmopolitan species (72 species). The main theme of western affinity of Taiwan flora is clearly indicated by almost 52% of the total flora (2069 species) which are also represented in China. The alliances of the flora are also pronounced with the Ryukyus and southern Japan (1618 species in common). However, the close relationship between Taiwan and Japan is through their mutual relation to the lowland flora of southern and eastern China. The tropical elements, mostly ranging from Malaysia to the Philippines, are well represented in the lowlands of Taiwan and particularly in the southernmost Hengchun Peninsula and the Lanyu Island off the southeast coast of Taiwan