Chromosomal evolution of <i>Gentiana</i> and <i>Jaeschkea</i> (<i>Gentianaceae</i>), with further documentation of chromosome data for 35 species from western China

Chromosome numbers were recorded for 63 populations of 34 species belonging to the genus <i>Gentiana</i> from the high altitude regions of western China. Counts for 22 species were reported for the first time and new numbers were found for <i>G. heleonastes</i> (2n = 36), <i>G. prattii</i> (2n = 20) and <i>G. pseudoaquatica</i> (2n = 40). Incorporating previous data, a complete series of gametic chromosome numbers from n = 6 to 24 and 26 was established for the genus, suggesting rapid karyotypic evolution by a combination of dysploidy and polyploidy. The cytotype 2n = 20 is proposed as the ancestral type in sect. <i>Chondrophyllae</i> s. l. The chromosome number 2n = 16 was found for <i>Jaeschkea microsperma</i> for the first time which, with previous reports of 2n = 18, 20 and 22, indicates that <i>Jaeschkea</i> is a typically dysploid genus.