Zygophylloideae is a subfamily of the family

Zygophyllaceae Zygophyllaceae is a family of flowering plants that contains the bean-caper and caltrop. The family includes around 285 species in 22 genera. Plants in the family Zygophyllaceae may be trees, shrubs, or herbs. They are often found in dry habit ...

. The subfamily comprises about 180 species of shrubs, subshrubs and herbs, found throughout arid parts of the Palaeotropics and into North and South America. , the division of the subfamily into genera is disputed, with between four and seven genera accepted by different sources.

Taxonomy

Molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

studies from 2000 onwards have repeatedly strongly supported the

monophyly In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...

of the subfamily Zygophylloideae. However, the division of the subfamily into genera remains disputed, . A study in 2000 showed that the genus ''

Zygophyllum ''Zygophyllum'' is the type genus of the flowering plant family Zygophyllaceae. The generic name is derived from the Greek language, Greek words ζυγόν (''zygon''), meaning "double", and φυλλον (''phyllon''), meaning "leaf". It refer ...

'', as then

circumscribed In geometry, a circumscribed circle for a set of points is a circle passing through each of them. Such a circle is said to ''circumscribe'' the points or a polygon formed from them; such a polygon is said to be ''inscribed'' in the circle. * Circum ...

, was

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

, with ''Augea'', ''Fagonia'' and ''Tetraena'' embedded within it. One response to this, published in 2018, was to expand ''Zygophyllum'' to include these three genera. , both

Plants of the World Online Plants of the World Online (POWO) is an online taxonomic database published by the Royal Botanic Gardens, Kew. History Following the Convention on Biological Diversity, the Royal Botanic Gardens in Kew launched Plants of the World Online i ...

and the

World Flora Online World Flora Online is an Internet-based compendium of the world's plant species. Description The World Flora Online (WFO) is an open-access database, launched in October 2012 as a follow-up project to The Plant List, with the aim of publishi ...

synonymize ''Augea'', ''Fagonia'' and ''Tetraena'' with ''Zygophyllum'', but retain ''Melocarpum'' and ''Miltianthus''. An alternative proposed in 2003 is to recognize six monophyletic genera (''Augea'', ''Fagonia'', ''Melocarpum'', ''Roepera'', ''Tetraena'', and ''Zygophyllum''). A

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

supporting this proposal is shown below. Sheahan in 2006 did not fully support the recognition of six genera within the Zygophylloideae. He accepted ''Tetraena'' only as a monotypic genus endemic to Inner Mongolia, and did not accept ''Roepera''. A 2008 study recognized neither ''Roepera'' nor ''Tetraena''. Its preferred cladogram is shown below.

Genera

Distribution and habitat

Members of the subfamily Zygophylloideae are generally adapted to arid conditions. They are found in dry or desert areas throughout the Palaeotropics, including Asia, northern Africa and Arabia, southwestern Africa, and Australia. In the broad

circumscription Circumscription may refer to: * Circumscribed circle * Circumscription (logic) *Circumscription (taxonomy) * Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthr ...

used by, for example, Plants of the World Online, the genus ''

'' extends into North and South America. File:Zygophyllum spinosum = Roepera spinosa (Zygophyllaceae) (37468785332).jpg, ''

Roepera spinosa ''Roepera'' is a genus of flowering plants in the family Zygophyllaceae, subfamily Zygophylloideae. It is native to Australia and south-western Africa, from Angola to South Africa. Description Species of ''Roepera'' are shrubs, subshrubs or herb ...

'', coastline of

Namaqua National Park Namaqua National Park is a South African national park situated on the edge of the Atlantic Ocean, Atlantic coast of Namaqualand (an area covering 440,000 km2 located within the semi-desert Succulent Karoo biome).Van Deventer, M. and J.A.J. ...

File:Zygophyllum ammophilum habit.jpg, ''

Roepera ammophila ''Roepera'' is a genus of flowering plants in the family Zygophyllaceae, subfamily Zygophylloideae. It is native to Australia and south-western Africa, from Angola to South Africa. Description Species of ''Roepera'' are shrubs, subshrubs or herb ...

'', Australia File:Zygophyllum Atriplicoides in Behbahan, Iran (2).jpg, ''

Zygophyllum atriplicoides ''Zygophyllum'' is the type genus of the flowering plant family Zygophyllaceae. The generic name is derived from the Greek words ζυγόν (''zygon''), meaning "double", and φυλλον (''phyllon''), meaning "leaf". It refers to the leaves, ...

'',

Behbahan Behbahan () is a city in the Central District of Behbahan County, Khuzestan province, Iran, serving as capital of both the county and the district. Etymology The origin of word 'Behbahan' can be traced back to two distinct ideas. Accord ...

, Iran File:Fagonia cretica.jpg, '' Fagonia cretica'', syn. ''Zygophyllum creticum'', Cartagena, Spain File:Zygophyllum dumosum.jpg, '' Zygophyllum dumosum'',

Negev Desert The Negev ( ; ) or Naqab (), is a desert and semidesert region of southern Israel. The region's largest city and administrative capital is Beersheba (pop. ), in the north. At its southern end is the Gulf of Aqaba and the resort town, resort city ...

References

{{Taxonbar, from1=Q6171985 Rosid subfamilies