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 ter ...

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 ...

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 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 swi ...

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 siste ...

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

, Micrairoideae,

Aristidoideae The Aristideae is the sole tribe of grasses in the monotypic subfamily Aristidoideae of the true grass family Poaceae. Its members are herbaceous annuals or perennials found in the tropics, subtropics and temperate zones. The tribe has over 300 ...

, and

Danthonioideae Danthonioideae is a mainly southern hemisphere subfamily of grasses, containing the single tribe Danthonieae and one unplaced genus, with altogether roughly 300 species. It includes herbaceous to partially woody perennial or annual (less common) ...

. It has no defined taxonomic rank but is used frequently because it refers to a well-defined

monophyletic group 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, ...

with a distinct ecology. Phylogeny of the PACMAD clade, with photosynthetic pathways for each subfamily:

References

Poaceae Photosynthesis Plant unranked clades {{Poaceae-stub