Chromosome variation in the genus Pinellia (Araceae) in China and Japan

The chromosome numbers of 23 populations belonging to seven species of Pinellia Tenore were counted. The basic chromosome number of all the species studied was x = 13, and the previously reported basic numbers x = 9 and x = 14 in P. ternata and P. cordata were not confirmed. Chromosome numbers of 2n = 26 in P. polyphylla and 2n = 78 in P. integrifolia are reported for the first time. Heptaploid (7x) and nonuploid (9x) are new ploidy levels reported for P. ternata, and hexaploid for P. cordata. Taxonomic, phylogenetic and phytogeographical inferences are made for the genus. Particular attention was given to P. ternata, the most widely distributed species in the genus, and considerable variation of chromosome number was found in its different populations. Based on chromosome studies of 11 populations of P. ternata, together with 12 populations reported in previous studies, the lower reaches of the Yangze River are identified as its centre of origin. From there it dispersed, with generation of hexaploid, heptaploid, octoploid and nonuploid forms.