Karyotype analysis in 21 plant families from the Qinghai–Tibetan Plateau and its evolutionary implications

The chromosome numbers and karyotypes of 105 accessions in 55 genera 75 species from 21 plant families growing on the Qinghai-Tibetan Plateau were investigated. For 31 species, we provided first insights into their chromosomal numbers and karyotype characteristics. Diploids and tetraploids existed in an altitudinal range from 1,500 to 4,851 m.a.s.l., while pentaploid, hexaploid, heptaploid, octaploid, and decaploid accessions tended to occur above 3,000 m.a.s.l. The frequency of polyploidy was relatively low below 3,000 m.a.s.l., indicating the relative stability of habitats on the Qinghai-Tibetan Plateau below 3,000 m.a.s.l. However, 80% of diploids occurred above 3,000 m, indicating that partial polyploids may be produced from intraspecific polyploidy. The difference in polyploidy frequency levels among the different habitats were striking, being about 40% in hillsides and wetland, approximately 25% of alpine meadow, meadow and shrublands, and 7% on benchland and wetlands.