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

Abstract

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.

DCDB: an updated online database of chromosome numbers of tribe Delphinieae (Ranunculaceae)

“…(1999) plus the results of the extensive search of reports published since 1999 to date, as well as the newly verified counts given in old publications. The current version of DCDB is updat-ed up to April 23, 2016, just the day after the online publication of the significant paper of Hong & al. (2016) that comprised 60 new chromosome reports from 20 species of Aconitum subg.…”

“…However, as new major/medium taxonomic rearrangements seem still necessary/possible [i.e., recognizing a new subgenus for the Delphinium anthriscifolium group, looking for a new placement for Aconitum fletcherianum G. Taylor-its recent accommodation in a new sect. Fletcherum by Tamura (1996) or in a new subgenus Tangutica by Kadota (2001) are considered not definitive (see Hong & al. 2016)-or a clarified status of Aconitum subg.…”

FISH-aimed karyotype analysis in Aconitum subgen. Aconitum reveals excessive rDNA sites in tetraploid taxa

“…Most taxa are diploid (2 n = 16) or tetraploid (2 n = 32), but triploid, pentaploid, hexaploid, and octoploid plants have been also detected (Simon et al 2001 ). Only diploid A. fletcherianum (possessing two large metacentric chromosome pairs and x = 6) has a different genome construction (Hong et al 2016 ). It seems puzzling that during 30 million years of evolution of so widely distributed and species-rich genus (Jabbour and Renner 2012 ), its karyotype uniformity has been preserved.…”

Phylogeny and reclassification of Aconitum subgenus Lycoctonum (Ranunculaceae)

“…Lycoctonum seems also quite abnormal in terms of karyological characters. Most recently Hong et al [ 10 ] reported the chromosome number of this species as 2 n = 12. This count represents a new base chromosome number of x = 6 for the genus Aconitum which otherwise has a uniform base chromosome number of x = 8.…”

“…fletcheranum is unique in Aconitum . There are two largest metacentric chromosome pairs in this species, whereas in all the other diploid taxa of the genus with available chromosomal data there is only one such chromosome pair, with the second largest pair being submetacentric [ 10 ].…”