Cytological studies on the Sino-Himalayan endemic Solms-laubachia (Brassicaceae) and two related genera

Abstract

The karyotypes of six species of Solms-laubachia and one each of Parrya and Desideria (Brassicaceae) from the Himalayan-Hengduan Mountains (Tibet, Sichuan and Yunnan provinces) were investigated. Chromosome counts of S. xerophyta, S. lanata, S. platycarpa and D. baiogoinensis are reported for the first time and found to be diploid with 2n = 14. Diploid counts were also made of S. retropilosa, a species previously known to be a tetraploid. The karyotype formulae of D. baiogoinensis, S. eurycarpa, S. pulcherrima, S. retropilosa, S. xerophyta and S. platycarpa are 2n = 14 = 6 m + 6sm + 2st, whereas those of S. lanata and P. nudicaulis are 2n = 14 = 6 m + 2sm + 6st and 2n = 14 = 8 m + 4sm + 2st, respectively. Karyotypes and counts of S. eurycarpa and S. pulcherrima are in agreement with prior studies. The relationships within Solms-laubachia and among the three genera are discussed. Speciation within Solms-laubachia may have been the result of primarily intrachromosomal variation at the diploid level, and the genus probably evolved within the Himalayan-Hengduan Mountains instead of migrating from other regions. © 2004 The Linnean Society of London.