The PACMAD clade (previously PACCMAD, PACCAD, or PACC
) is one of two major
lineages (or
clades) of the true grasses (
Poaceae), 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 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 s ...
,
Arundinoideae,
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 i ...
,
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