Native and exotic species of terrestrial earthworms (Oligochaeta) in Taiwan with reference to Northeast Asia.

Of the 35 nominal species of terrestrial earthworms (Oligochaeta) reported from Taiwan, there are 30 species of the Megascolecidae, two species of the Lumbricidae, and 1 species each for the Moniligastridae, Glossoscolecidae, and Octochaetidae. The genera Amynthas and Metaphire of the Megascolecidae are dominant and include 27 species, of which 12 species are native. Among these 35 species, the 12 native species occur primarily in hills and mountains of the island, where natural environments (forests) still remain, or in areas relatively less disturbed by humans. The other 23 species are exotic, including 4 species with presumed origins from America and Europe, four species from Southeast Asia, and 15 species from southern China. They occur in disturbed environments (urban areas and cultivated lands) on the plains and in some hill and mountainous areas. Endemism based on the nominal species in Taiwan is 34.3%, which is much lower than 74.2% for Hainan Island, 78.1% for China, 65.0% for Japan, 60.0% for Korea, and 37.0% for the Ryukyus. The native species of Amynthas and Metaphire in Taiwan are apparently offshoots of the oligochaete fauna of southern China, resulting from dispersion differentiation.