Karyology of Aconitum subgenus Lycoctonum (Ranunculaceae) from China, with a report of the new base chromosome number x = 6 in the genus Aconitum

In order to gain better knowledge of the number and morphology of chromosomes in Aconitum subgen. Lycoctonum in China, 60 populations belonging to 20 species were cytologically studied. Chromosome numbers of six species ( A. apetalum, A. finetianum, A. fletcheranum, A. longecassidatum, A. umbrosum and A. wangyedianense ) are here reported for the first time. One species, A. fletcheranum , has 2n = 12, and thus is a diploid based on x = 6, a new base chromosome number for the genus Aconitum . Most of the remaining taxa are diploid (2n = 16) based on x = 8, but five taxa ( A. angustius, A. brevicalcaratum var. brevicalcaratum, A. brevicalcaratum var. parviflorum, A.chrysotrichum and A. crassiflorum ) are tetraploid with 2n = 32, and one species ( A. apetalum ) is hexaploid with 2n = 48, the highest ploidy level currently known in the subgenus. Disregarding differences in the presence or absence and number of satellites, the karyotypes of all the 2n = 16 species are quite uniform (2n = 2m + 6sm + 8st), but A. novoluridum , the only species of A . section Alatospermum , has an intrachromosomally less asymmetric karyotype (2n = 2m + 14sm), which lends further support for the primitive condition of its section as inferred from gross‐morphology. Chromosomal variation in the subgenus and the relationships of some of the species are discussed.