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

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

s) of the true grasses (

Poaceae Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns an ...

), 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 t ...

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. Its sister group is the PACMAD clade; contrary ...

. 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. The name of the clade comes from the first initials of the included subfamilies Panicoideae,

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 sister ...

, Chloridoideae, Micrairoideae, 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