Traditionally the sympetalous, Eurasian Crassulaceae are classified in four genera, but combined biosystematic, molecular and chemotaxonomic studies indicate that sympetaly evolved at least eight times independently in European Crassulaceae. Morphologically Umbilicus is very distinct and at the molecular level it also represents a distinct evolutionary lineage. The other three sympetalous genera evolved from the large paraphyletic genus Sedum. Of these three taxa Pistorinia represents a monophyletic lineage, whereas Mucizonia and Rosularia, are polyphyletic. The results of the hybridization experiments and molecular analyses justify the transfer of the Mucizonia species to the polypetalous Sedum series Dasyphylla and S. series Pedicellata, respectively. Cytological, phytochemical and molecular evidence indicate that Rosularia sect. Rosularia and R. sect. Chrysantha represent independent evolutionary lineages. Moreover, cpDNA restriction site analysis indicates a close relationship between R. sect. Chrysantha and the comparium comprising Prometheum pilosum, P. sempervivoides and P. tymphaeum which were formerly included in Sedum. Consequently R. sect. Chrysantha was transferred to Prometheum. Phytochemically, however, this genus is rather diverse. In addition to these six taxa, sympetaly evolved independently in Sedum lagascae, which is closely related to polypetalous S. villosum, and in S. series Alsinefolia, which in our molecular analyses appears to be related to polypetalous S. hispanicum.
’T Hart, H., Van Ham, R. D. H. J., Stevens, J. F., Elema, E. T., Van Der Klis, H., & Gadella, T. W. J. (1999). Biosystematic, molecular and phytochemical evidence for the multiple origin of sympetaly in Eurasian Sedoideae (Crassulaceae). Biochemical Systematics and Ecology, 27(4), 407–426. https://doi.org/10.1016/S0305-1978(98)00098-2