Gomphrenoideae

The Gomphrenoideae are a subfamily of the Amaranthaceae.
The stamens have anthers with only one lobe (locule) and two pollen sacs. Many species show C4-photosynthesis pathway.
The center of diversity lies in Central America, Mexico and the dry forests and thorn bush savannas of South America.
Systematics.
The subfamily Gomphrenoideae was first published in 1893 by Hans Schinz (in: Engler und Prantl (Eds.): "Die Natürlichen Pflanzenfamilien" vol. 3, 1a, p. 97).
According to phylogenetic research by Sanchez Del-Pino (2009), the subfamily Gomphrenoideae Schinz is regarded as a monophyletic taxon with 19 genera and about 300-400 species. The traditional classification with two tribes (Gomphreneae and Pseudoplantageae) does not reflect the phylogenetic relationship in this group. Three clades can be recognized.:
Iresinoids.
This is the sister clade of the two other clades.
Alternantheroids.
 carbon fixation evolved independently in the genera "Alternathera", which also contains and – intermediate species, and "Tidestromia".
Gomphrenoids.
One large clade within this group, containing the genera "Froelichia", "Guilleminea", "Blutaparon", some "Gomphrena" species, and probably "Gossypianthus" and "Lithophila", has acquired the carbon fixation pathway. Some of these species occur at unusually high altitudes in the Andes, in cooler conditions than their relatives.