Phylogenetic relationships and evolution of Crassulaceae inferred from matK sequence data

Chloroplast gene matK sequence data were used to estimate the phylogeny of 112 species of Crassulaceae sampled from 33 genera and all six recognized subfamilies. Our analyses suggest that Eve of six subfamilies recognized in the mast recent comprehensive classification of the family are not monophyletic. Instead, we recovered a basal split in Crassulaceae between the southern African Crassula clade (Crassuloideae) and the rest of the family (Sedoideae). These results are compatible with recent studies of cpDNA restriction site analyses. Within Sedoideae, four subclades were also recovered: Kalanchoe, Leucosedum, Acre, and Aeonium; evidence also exists for a Telephium clade and Sempervivum clade. The genus Sedum is highly polyphyletic with representatives spread throughout the large Sedoideae clade. Sympetaly and polymerous flowers have arisen multiple times in Crassulaceae and thus are not appropriate characters upon which to base subfamilial limits, as has been done in the past. One floral character haplostemy, appears to be confined to the well-supported Crassula clade. Our analyses suggest a southern African origin of the family, with subsequent dispersal northward into the Mediterranean region. From there, the family spread to Asia/eastern Europe and northern Europe; two separate lineages of European Crassulaceae subsequently dispersed to North America and underwent substantial diversification. Our analyses also suggest that the original base chromosome number in Crassulaceae is x = 8 and that polyploidy has played an important role in seven clades. Three of these clades are exclusively polyploid (Sempervivum clade and two subclades within the Kalanchoe and Aeonium clades), whereas four (Crassula, Telephium, Leucosedum, and Acre clades) comprise both diploid and polyploid taxa. Polyploidy is particularly rampant and cytological evolution especially complex in the Acre clade.