Succulent leaved plants. Unlike the other two smaller subfamilies, which are highly derived, Sempervivoideae retain the basic features of the family Crassulaceae. The Sempervivoideae contain many familiar horticultural plants, such as Sedum.
Taxonomy
Sempervivoideae has taxonomic priority over its synonym, Sedoideae, and is related to the other Crassulaceae subfamilies, as shown in this cladogram;
Subdivisions (tribes)
Six clades within Crassulaceaeare are segregated into the five tribes with about thirty genera.
and their relationship is shown in the cladogram: However, given the difficulty of establishing a stable classification, some authors prefer larger groupings, e.g.;
Telephinae
Sedinae
Semperviviae, Aeonieae and Sedeae are definable only by plesiomorphic features, with their genera all derived from within Sedum. Segregates of Sedum occur in each of these, but lack sufficient features to allow them to be allocated to definitive genera.
The Telephieae genera consist of former infrageneric taxa of Sedum, and are distributed primarily in East Asia. Defined by 5-merous flowers, free petals, flat, dentate leaves and tuberous roots or thickened rhizomes. Leaves usually in rosettes, except Hylotelephium, petals often spotted, autumn flowering. The taxonomy remains unstable, with species Orostachys embedded within both Meterostachys and Hylotelephium. It contains about 6 genera, with 50 species, including: It is likely that diversification of the tribe occurred at the time of the formation of the Himalayas.
The Umbeliceae occur mainly in temperate areas of Asia, flowering in spring to early summer, with about 4−5 genera and 100 species. Aizopsis is included by some authors in Phedimus. The genera are among those that have been segregated from Sedum, including:
Aizopsis Grulich
Phedimus Raf. c. 20 sp., Asia, Europe
Pseudosedum A.Berger c. 10 sp., C Asia
Rhodiola L. c. 60 sp., Himalaya, Siberia, Europe, N America
Semperviveae have acuminate leaves and polymerous flowers. Two to three genera, derived from within Sedum, c. 275 species. Earlier treatments considered Jovibarba a section of Sempervivum but has subsequently been demonstrated to be a separate genus.
Jovibarba Opiz
Petrosedum Grulich c. 21 sp. Euro-Mediterranean
Sempervivum L.
Aeonieae Thiede ined.
Aeonieae, whose distribution is primarily Macaronesia, have polymerous flowers, and include genera derived from within Sedum, with about 3 genera and 70 species, including:
Sedeae is the largest of these and contains two sister clades, Leucosedum and Acre. It contains about 12 genera, mainly derived from within Sedum, and 520 species. Genera are often treated as two separate clades. Of these, while the larger Acre is robust, Leucosedum remains paraphyletic. The genera included are:
Leucosedum clade
Genera derived from European and Mediterranean Sedum subg. Gormania, with two western North American genera.
Afrovivella A.Berger
Dudleya Britton & Rose
Pistorinia DC.
Prometheum H.Ohba c. 8 sp., E Europe, C Asia
Rosularia Stapf c. 20 sp., E Europe, Himalaya, Altai
Sedum L. c. 470 sp. N hemisphere, S. America, N Africa
Genera
Given the monophyly demonstrated for Aeonieae and Semperviveae, it has been recommended that those species of Sedum originally found in those tribes, be removed from the genus and reassigned. This includes Sedum series Rupestria from Semperviveae, but collectively account for only a small fraction of the genus. While restricting Sedum to Sedeae simplifies the infrafamilial structure of the genus, its species remain distributed within both clades of this tribe.
