| Didiereaceae | |
|---|---|
 | |
| Alluaudia montagnacii | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Caryophyllales |
| Family: | Didiereaceae Radlk.[1] |
| Subfamilies | |
Didiereaceae is afamily offlowering plants found in continentalAfrica andMadagascar.It contains 20 species classified in three subfamilies and six genera. Species of the family aresucculent plants, growing in sub-arid to arid habitats. Several are known asornamental plants in specialist succulent collections. The subfamily Didiereoideae isendemic to the southwest of Madagascar, where the species are characteristic elements of thespiny thickets.
The family was long considered entirely endemic to Madagascar until the generaCalyptrotheca,Ceraria, andPortulacaria from the African mainland were included.[2]Molecular phylogenetic analysis confirmed themonophyly of the family and its three subfamilies:[3]
| Didiereaceae |
| ||||||||||||
The family is closely related to theNew World familyCactaceae (cacti), sufficiently closely so that species of Didiereaceae can begrafted successfully on some cacti.[3]
Contains only one genus,Calyptrotheca, with two species found in tropicalEast Africa.[3]
This subfamily is endemic to Madagascar, where it is found in thespiny thickets of the dry southwest. The plants arespinysucculentshrubs andtrees from 2–20 m tall, with thick water-storing stems andleaves that aredeciduous in the longdry season. All of the species exceptAlluaudiopsis have a distinct youth form. They start as small procumbent shrubs but eventually a dominant stem is produced that becomes a trunk. The trunk later branches forming a crown and the basal branches die off.[4] All species aredioecious (Decarya female-dioecious). The plants have different long-shoots and short-shoots (brachyblasts). Long-shoot leaves are soon deciduous, but brachyblasts form in the leaf axils and from them grow small leaves that appear singly or in pairs and are accompanied by conical spines (much like theareoles found incacti). The flowers are unisexual (except fromDecarya) and radially symmetric, made up of fourtepals with two basal bracts. Flowers rarely occur singly. They usually develop in branched clusters that emerge instead of leaves from the brachyblasts.[4]
There are four genera with eleven species:
AlluaudiopsisHumbert &Choux 1934
Key to the genera of Didieroideae:
| 1 | Spines in groups of four or more: | Didierea |
| - | Spines single or in pairs: | → 2 |
| 2 | Shoots striking zigzagged, spines short conical: | Decarya |
| - | Shoots not zigzagged, spines long conical to needle-like: | → 3 |
| 3 | Shrubs strongly branched, leaves lanceolate: | Alluaudiopsis |
| - | Shrubs little branched, leaves either ovate to circular or scale-like and awl-shaped: | Alluaudia |
Contains one genus,Portulacaria, with seven species, distributed inSouthern Africa. Species formerly considered in the separate genusCeraria are now included inPortulacaria.[3]
