Four new species of terrestrial earthworms belonging to the genusAmynthas(Megascolecidae: Oligochaeta) from Taiwan with discussion on speculative synonyms and species delimitation in oligochaete taxonomy

This paper describes four new species of earthworms, Amynthas shinanmontis sp. nov., Amynthas chilanensis sp. nov., Amynthas bilineatus sp. nov., and Amynthas cruxus sp. nov. from Taiwan. Amynthas shinanmontis is sexthecate and parthenogenetic with individuals with various levels of degeneration of spermathecae and male reproductive organs. It occurs at elevations of 1700–2700 m in the Central Mountain Range in southern Taiwan. Amynthas bilineatus and A. chilanensis are athecate and also parthenogenetic. They occur, respectively, at elevations of 1000 m in the central region and 1325 m in the northeastern region of Taiwan. Amynthas cruxus is octothecate, amphimictic, and occurs at elevations of 900–1700 m in southern Taiwan. This paper also discusses confusion and dilemma caused by uncertain, speculative synonyms and parthenogenetic morphs in species delimitation in oligochaete taxonomy, and recommends the use of absolute synonyms and phylogenetic species concept.