Didiereaceae is a family of found in continental Africa and Madagascar.
It contains 20 species classified in three subfamilies and six genera. Species of the family are , growing in sub-arid to arid habitats. Several are known as in specialist succulent collections. The subfamily Didiereoideae is endemic to the southwest of Madagascar, where the species are characteristic elements of the spiny thickets.
Systematics
The family was long considered entirely endemic to Madagascar until the genera
Calyptrotheca,
Ceraria, and
Portulacaria from the African mainland were included.
[ ] Molecular phylogenetic analysis confirmed the
monophyly of the family and its three subfamilies:
The family is closely related to the New World family Cactus (cacti), sufficiently closely so that species of Didiereaceae can be grafting successfully on some cacti.
Calyptrothecoideae
Contains only one genus,
Calyptrotheca, with two species found in tropical
East Africa.
Didiereoideae
This subfamily is endemic to Madagascar, where it is found in the spiny thickets of the dry southwest. The plants are spiny
Succulent plant and
from 2–20 m tall, with thick water-storing stems and
leaf that are
deciduous in the long
dry season. All of the species except
Alluaudiopsis 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.
[Rauh, W. 1983. The morphology and systematic position of the Didiereaceae of Madagascar. Bothalia 14(3/4): 839–843.] All species are
dioecious (
Decarya female-dioecious). The plants have different long-shoots and short-shoots (
). 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 the
found in
cactus). The flowers are unisexual (except from
Decarya) and radially symmetric, made up of four
tepals with two basal bracts. Flowers rarely occur singly. They usually develop in branched clusters that emerge instead of leaves from the brachyblasts.
There are four genera with eleven species:
Alluaudia
-
Alluaudia ascendens
-
Alluaudia comosa
-
Alluaudia dumosa
-
Alluaudia humbertii
-
Alluaudia montagnacii – probably a natural hybrid of A. ascendens and A. procera
-
Alluaudia procera – quite easy grown and the most frequent species in cultivation
Alluaudiopsis
-
Alluaudiopsis fiherensis
-
Alluaudiopsis marnieriana
Decarya
Didierea
Key to the genera of Didieroideae:
| Didierea |
| → 2 |
| Decarya |
| → 3 |
| Alluaudiopsis |
| Alluaudia |
|
Portulacarioideae
Contains one genus,
Portulacaria, with seven species, distributed in
Southern Africa. Species formerly considered in the separate genus
Ceraria are now included in
Portulacaria.
==Gallery==
