A molecular study of the relationship between the coenagrionid genera Erythromma and Cercion, with the creation of Paracercion gen. nov. for the East Asiatic "Cercion" (Zygoptera: Coenagrionidae)

The ribosomal DNA genes (18S, 5.8S) and internal transcribed spacers (ITS1, ITS2) of 5 representatives of "Cercion" occurring in East Asia were examined and compared with west-palaearctic "Cercion" lindenii, Erythromma najas (2 populations), E. viridulum, some true Coenagrion species, and with Enallagma and Ischnura as outgroups. The molecular phylogenetic tree confirms the position of H. Heidemann & R. Seidenbusch (1993, Die Libellenlarven Deutschlands und Frankreichs, Bauer, Keltern) that Cercion lindenii belongs in Erythromma, and consequently, the binomen Erythromma lindenii is accepted. Regarding the "oriental" group for which, under the new situation, the name Cercion is no longer available, the genus name Paracercion gen. n. is introduced. This is supported by molecular evidence and by some morphological traits. A morphological basis for setting apart the new genus from Erythromma is thus achieved, but its delimitation from Coenagrion remains to be defined.