Nikulin V. Yu., Gontcharov A.A.
Botanicheskii zhurnal 2017; 102(3): 309-328
Sedum is the most species-rich and taxonomically complex genus of the family Crassulaceae. The genus comprises ca. 420 species displaying notable morphological diversity and homoplasy of many features traditionally used to delineate crassulacean genera. Therefore it is impossible to characterize Sedum phenotypically. Artificial nature of Sedum was recognized long time ago, it was characterized as a «catch-all» taxon absorbed many species that do not fall into diagnoses of other genera. The phylogenetic structure of Sedum and its relationship with allied genera are poorly understood. Therefore, we carried out phylogenetic analysis of the tribes Aeonieae, Semperviveae, and Sedeae accommodating Sedum species based on 102 partial matK gene sequences of chloroplast DNA. To achieve a better resolution of the tree topology we increased the number of the positions analyzed by including the internal transcribed spacer (ITS) rDNA sequences. Our molecular phylogenetic data corroborated results of previous studies based on other markers and limited datasets. The analysis revealed that the majority of Sedum species is placed in the clades Acre and Leucosedum comprising the tribe Sedeae. Besides Sedum, this tribe accommodates a number of genera that were mostly embedded among Sedum species. Our results suggest highly polyphyletic nature of Sedum and its relatives and call for re-evaluation of their genus concepts.
