Biosystematic studies in Sedum (Crassulaceae) from Turkey. 4. The cytology of Sedum subsect. Spathulata Boriss.

The diploid cytotypes of the species of Sedum series Involucrata and S. series Propontica of S. subsect. Spathulata differ more than five-fold in nuclear DNA amount, even though some occur in similar habitats and sometimes in mixed populations. Morphologically the two series are quite similar, but the basic chromosome numbers and karyotypes differ considerably, and they are probably only distantly related. The dysploid series in S. series Propontica, ranging from x-1 to x=s, is not a result of a simple series of successive Robertsonian translocations, but involves different kinds of chromosomal rearrangements as well. The 2C value of S. obtusifolium i (x-6) with the chromosome number 2n = 30 would indicate an octoploid (8x) level of ploidy, but the karyotype structure offers no explanation for the implicit loss of 18 chromosomes.