The PACMAD clade (previously PACCMAD, PACCAD, or PACC) is one of two major lineages (or

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

s) of the true grasses (

Poaceae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivate ...

), regrouping six subfamilies and about 5700 species, more than half of all true grasses. Its

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

is the

BOP clade The BOP clade (sometimes ''BEP clade'') is one of two major lineages (or clades) of undefined taxonomic rank in the grasses (Poaceae), containing more than 5,400 species, about half of all grasses. Well-known members of this clade include rice, ...

. The PACMAD lineage is the only group within the grasses in which the C₄ photosynthesis pathway has evolved; studies have shown that this happened independently multiple times.

Phylogeny

The name of the clade comes from the first initials of the included subfamilies

Panicoideae Panicoideae is the second-largest subfamily of the grasses with over 3,500 species, mainly distributed in warm temperate and tropical regions. It comprises some important agricultural crops, including sugarcane, maize (or corn), sorghum, and s ...

Arundinoideae The Arundinoideae are a subfamily of the true grass family Poaceae with around 40 species, including giant reed and common reed. Unlike many other members of the PACMAD clade of grasses, the Arundinoideae all use C3 photosynthesis. Their sist ...

Chloridoideae Chloridoideae is one of the largest subfamily, subfamilies of Poaceae, grasses, with roughly 150 genera and 1,600 species, mainly found in arid tropical or subtropical grasslands. Within the PACMAD clade, their sister group is the Danthonioideae. ...

Micrairoideae Micrairoideae is a subfamily of the grass family Poaceae, distributed in tropical and subtropical regions. Within the PACMAD clade, it is sister to subfamily Arundinoideae. It includes roughly 190 species in nine genera. A phylogenetic classifi ...

, Aristidoideae, and Danthonioideae. It has no defined taxonomic rank but is used frequently because it refers to a well-defined monophyletic group with a distinct ecology. Phylogeny of the PACMAD clade, with photosynthetic pathways for each subfamily:

References

Poaceae Photosynthesis Plant unranked clades {{Poaceae-stub