The subgenera are given in different colours. The numbers give the haploid chromosomal numbers of the species. Numbers in yellow circles are the haploid chromosomal numbers of unknown starting species. The diagram shows that the phylogenetic tree of species belonging to one genus cannot be depicted as a divergence scheme (exclusively dichotomous ramifications), but has to be illustrated as a network with numerous convergences, that are consequences of hybridizations (H. and M. LEWIS, 1955, L. D. GOTTLIEB, 1983 according to H. LEWIS, 1980).