Cytological study of begonia sect. coelocentrum (begoniaceae)

Abstract

Begonia sect. Coelocentrum is a characteristic plant group in the limestone karsts of southern China and northern Vietnam and yet previous chromosome information is restricted to ca. 50 species and their karyotypes have never been investigated. Here we report the cytological investigations of 15 species of sect. Coelocentrum, including four karyotype analyses that are the first report in sect. Coelocentrum, ten species reported cytologically for the first time, and five species that were re-examined. Incorporating recent and present studies, chromosome numbers of 56 of the 82 species in sect. Coelocentrum are now available. Among the 56 species, 55 have a stable and common chromosome number of 2n=30, with a few species showing aneuploidy numbers of 2n=31, 32, 33, 35, 36, and a triploid number of 2n=45. Karyotypic formula of the four investigated species are uniform as 2n=30=8m+22sm(st). Based on our and previous studies, the chromosome evolution in Begonia sect. Coelocentrum is discussed.