Karyological studies on some species of radula (radulaceae, jungermanniopsida, marchantiophyta)

Karyological observations were made on 16 species of the genus Radula (Jungermanniopsida: Radulaceae) from China and Singapore. The chromosome number n = 8 was found in all Radula species investigated. The chromosome numbers of ten species belonging to six sections of two subgenera, i.e., Radula acuminata Steph. (Sect. Epiphyllae Castle ex Grolle), R. acuta Mitt. (Sect. Acutifoliae Castle ex Grolle), R. amoena Herzog (Sect. Acutifoliae), and R. anceps Sande Lac. (Sect. Acutifoliae), R. cavifolia Hampe ex Gottsche et al. (Sect. Cavifolium K.Yamada), R. formosa (Meissn.) Nees (Sect. Amentulosae Castle ex Grolle), R. gedena Gottsche ex Steph. (Sect. Epiphyllae), R. inouei K.Yamada (Sect. Radula), Radula onraedtii K.Yamada (Sect. Radula), and R. philippinensis K.Yamada (Sect. Dichotomae Castle & Grolle), are reported for the first time. The results for Radula javanica Gottsche (Sect. Radula), R. kojana Steph. (Sect. Acutifoliae), R. okamurana Steph. (Sect. Radula), and R. oyamensis Steph. (Sect. Radula) confirmed previous records. The chromosome counts in Radula constricta Steph. (Sect. Radula) (n = 8) and R. retroflexa Tayler (Sect. Retroflexa K.Yamada) (n = 7, 8) differ from earlier reports. In addition, karyotypes of five species, Radula cavifolia, R. constricta, R. javanica, R. inouei and R. retroflexa, were presented. The length and width of the largest chromosomes and smallest ones are provided. The karyotypes of Radula constricta are sometimes variable in different populations. Our results reveal that the chromosome numbers and karyotypes seem to have little taxonomic value in the infrageneric divisions of Radula.