Belongs within: Fabidae.
Contains: Cunoniaceae, Elaeocarpaceae.
The Oxalidales are a clade of flowering plants supported by molecular analyses. Many members of the clade are tropical trees and shrubs, but the clade also includes the prominent herbaceous genus Oxalis, the sorrels, a number of species of which are invasive weeds in many parts of the world. The Oxalidaceae also include the small tree genus Averrhoa, of which the carambola A. carambola and bilimbi A. bilimbi are cultivated for their edible fruit; the acidic fruit of A. bilimbi are more commonly used in cooking than eaten raw. Dapania is an Old World tropical genus of lianas with racemose inflorescences and fruits dehiscing into a five-pointed star.
The Connaraceae are a tropical family whose members are commonly lianas or scandent shrubs with alternate, pinnate leaves and follicular fruits. The Huaceae are a small family of trees and lianes of uncertain affinities found in central Africa, members of which have a distinct smell of garlic.
Members of the clade containing Cunoniaceae, Elaeocarpaceae, Brunellia and Cephalotus have a valvate calyx that is postgenitally coherent by hairs (Angiosperm Phylogeny Web). Cephalotus follicularis of south-western Australia is a herb with leaves modified into insect-catching lidded pitchers. Brunellia is a Neotropical montane genus of trees with usually odd-pinnately compound leaves and bearing apetalous flowers.
Cunoniaceae and friends
Published 30 November 2010
The plant order Cunoniales was first established in 1926 to include plants with similar flowers to the Saxifragales but that were primarily woody rather than herbaceous (Dickison 1975). Woodiness vs. herbaceousness is no longer considered that significant a feature in plant classification (sometimes you can find both in the same genus) and the content of the order has varied between classifications*. Today, the type family Cunoniaceae is included in the order Oxalidales and a taxon “Cunoniales” is no longer used as such. However, one of the two basal clades within the Oxalidales includes the Cunoniaceae and two ex-Cunoniales genera placed in their own families, Cephalotus and Brunellia, together with the family Elaeocarpaceae (previously in its own order) (Matthews & Endress 2002). With the notable exception of Cephalotus, the members of this clade are mostly shrubs or trees. Economically, the clade is not overly significant: some species are used for wood; some have good reputations as honey sources for bees; a few produce edible fruits but do not appear to have been systematically cultivated for them. Members of all families bear their flowers clustered into (most often cymose) inflorescences; the size of individual flowers in the inflorescences varies between species. Brunellia and Cephalotus both produce flowers with thick sepals and no petals; in the other two families, petals may be present or absent (Matthews & Endress 2002).
*As have most flowering plant “orders”. There’s a reason why order-level taxa don’t get much day-to-day use among botanists compared to families.
.The clade formed by these four families has a distinctly southern distribution in southern Africa, South and Central America, south-east Asia, Australia and New Zealand. Elaeocarpaceae are absent from continental Africa but are present in Madagascar. Also, while currently absent from India, they have been recorded from the fossil record there (Crayn et al. 2006). The Cunoniaceae include about 300 species, half in the genus Weinmannia, whereas the Elaeocarpaceae include about 600 species. Molecular studies have shown that an Australian radiation of dry-habitat shrubs previously regarded as the family Tremandraceae is in fact a subclade of the otherwise mostly rainforest-inhabiting Elaeocarpaceae (Crayn et al. 2006). Interestingly, the molecular dating study by Crayn et al. (2006) suggests that the ‘Tremandraceae’ developed scleromorphy (a suite of adaptations such as hardened leaves that are usually associated with arid habitats) some time before the Australian continent developed its current arid climate. While this may seem counter-intuitive, it is worth pointing out that the fossil record supports the same thing in the evolution of the genus Banksia (Mast & Givnish 2002). It has been suggested that scleromorphy in these groups was therefore not originally an adaptation for arid living, but for growing in the poor soils of the Palaeogene Australian rainforest.
The oddest member of this clade, however, has to be the Albany pitcher plant, Cephalotus follicularis. Restricted to the south-west corner of Western Australia, this plant bears a superficial resemblance to pitcher plants from other parts of the world, the mostly Indomalayan Nepenthaceae and the North American Sarraceniaceae. All three of these families have evolved the pitcher morphology independently, and can in fact be placed in separate subclasses: Cephalotus in the Rosidae, the Nepenthaceae in the Caryophyllidae and the Sarraceniaceae in the Asteridae. In the Nepenthaceae, the pitchers are developed from trendrils at the ends of the leaves; in the other two families, the entire leaves form the pitchers growing from a ground-level rhizome. In Cephalotus, only the outer leaves of an individual plant are developed into pitchers; the inner leaves remain flat and simple.
Systematics of Oxalidales
<==Oxalidales [Cunoniales]
| i. s.: Platydiscus peltatusXR12
|--HuaceaeWM09
| |--AfrostyraxCD07
| `--Hua gaboniiXR12, WM09
`--+--+--+--CunoniaceaeWM09
| | `--+--ElaeocarpaceaeWM09
| | `--Cephalotus [Cephalotaceae, Cephalotales]WM09
| | `--C. follicularisWM09
| `--Brunellia [Brunelliaceae]XR12
| |--B. comocladiifoliaJ87
| | |--B. c. ssp. comocladiifoliaJ87
| | `--B. c. ssp. domingensisJ87
| |--B. goudotiiR96
| `--B. vulgarisC55
`--+--ConnaraceaeWM09
| |--Jollydora [Jollydoroideae]T00
| |--RoureaB00
| | |--R. brachyandraB00
| | `--R. splendensT-W89
| |--Connaracanthium roureoides Conwentz 1886CBH93
| |--CnestisCBH93
| `--Connarus [Connaroideae]WM09
| `--C. conchocarpusWM09
`--Oxalidaceae [Averrhoeaceae]XR12
| i. s.: Oxalidites brachysepalus Caspary 1887CBH93
| Bilimbia Rchb. 1837KC01
| AverrhoitesR06
|--+--DapaniaXR12
| `--AverrhoaXR12
| |--A. bilimbiP88
| `--A. carambolaXR12
`--Oxalis Linnaeus 1753XR12, A61 [incl. OxysD01]
|--O. acetosellaC06
|--O. albicansH93
| |--O. a. ssp. albicansH93
| |--O. a. ssp. californicaH93
| `--O. a. ssp. pilosaH93
|--O. ausensisCV06
|--O. cernuaC06
|--O. corniculata Linnaeus 1753A61
| |--O. c. var. corniculataA61
| |--O. c. var. ciliifera (Cunn.) Hook. f. 1852 (see below for synonymy)A61
| |--O. c. var. crassifolia (Cunn.) Hook. f. 1852 [=O. crassifolia Cunn. 1839]A61
| `--O. c. var. microphylla Hook. f. 1852 [incl. O. exilis Cunn. 1839]A61
|--O. dillenii Jacq. 1794CD07
|--O. eggersiiJ87
|--O. hirtaC06
|--O. hunsbergensisCV06
|--O. laciniataD03
|--O. lactea Hook. 1836 [incl. O. cataractae Cunn. 1839, O. novae-zelandiae Gand. 1913]A61
|--O. latifolia [incl. O. martiana]H93
|--O. laxaH93
|--O. luederitziiCV06
|--O. magellanica Forst. f. 1789A61
|--O. micranthaH93
|--O. oreganaH93
|--O. perennansB00
|--O. pes-capraeM99
|--O. pseudo-cernuaCV06
|--O. purpurea [incl. O. variabilis]H93
|--O. rubraH93
|--O. schaeferiCV06
|--O. stricta Linnaeus 1753A61 (see below for synonymy)
|--O. suksdorfiiH93
|--O. trilliifoliaH93
`--O. tuberosaS00
Oxalis corniculata var. ciliifera (Cunn.) Hook. f. 1852 [=O. ciliifera Cunn. 1839; incl. O. tenuicaulis Cunn. 1839]A61
Oxalis stricta Linnaeus 1753A61 [=O. corniculata var. strictaC06; incl. O. ambigua Rich. 1832A61, O. divergens Cunn. 1839A61, O. lacicola Cunn. 1839A61, O. propinqua Cunn. 1839A61, O. urvillei Cunn. 1839A61]
*Type species of generic name indicated
References
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