Editing Monocotyledon (section)

=== Subdivision===

While the monocotyledons have remained extremely stable in their outer borders as a well-defined and coherent monophylectic group, the deeper internal relationships have undergone considerable flux, with many competing classification systems over time.<ref name=Kubitzmmonohist/>

Historically, [[George Bentham|Bentham]] (1877), considered the monocots to consist of four [[alliance (taxonomy)|alliances]], Epigynae, Coronariae, Nudiflorae and Glumales, based on floral characteristics. He describes the attempts to subdivide the group since the days of [[John Lindley|Lindley]] as largely unsuccessful.{{sfn|Bentham|1877}} Like most subsequent classification systems it failed to distinguish between two major orders, [[Liliales]] and [[Asparagales]], now recognised as quite separate.{{sfn|Fay|2013}} A major advance in this respect was the work of [[Rolf Dahlgren]] (1980),{{sfn|Dahlgren|1980}} which would form the basis of the [[Angiosperm Phylogeny Group]]'s (APG) subsequent modern classification of monocot families. Dahlgren who used the alternate name [[Lilliidae]] considered the monocots as a [[Subclass (biology)|subclass]] of [[angiosperms]] characterised by a single cotyledon and the presence of triangular protein bodies in the [[sieve tube]] [[plastids]]. He divided the monocots into seven [[Order (biology)|superorders]], Alismatiflorae, Ariflorae, Triuridiflorae, [[Liliiflorae]], Zingiberiflorae, Commeliniflorae and Areciflorae. With respect to the specific issue regarding Liliales and Asparagales, Dahlgren followed [[Herbert Huber (botanist)|Huber]] (1969){{sfn|Huber|1969}} in adopting a [[Lumpers and splitters|splitter]] approach, in contrast to the longstanding tendency to view [[Liliaceae]] as a very broad [[sensu lato]] [[Family (biology)|family]]. Following Dahlgren's untimely death in 1987, his work was continued by his widow, [[Gertrud Dahlgren]], who published a revised version of the classification in 1989. In this scheme the [[suffix]] ''-florae'' was replaced with ''-anae'' (''e.g.'' [[Alismatanae]]) and the number of superorders expanded to ten with the addition of Bromelianae, Cyclanthanae and Pandananae.{{sfn|Dahlgren|1989}}

Molecular studies have both confirmed the [[monophyly]] of the monocots and helped elucidate relationships within this group. The [[Angiosperm Phylogeny Group|APG]] system does not assign the monocots to a taxonomic rank, instead recognizing a monocots clade.{{sfn|Chase et al| 1995}}{{sfn|Chase et al|2000}}{{sfn|Davis et al|2004}}{{sfn|Soltis|Soltis|2004}} However, there has remained some uncertainty regarding the exact relationships between the major lineages, with a number of competing models (including APG).{{sfn|Zeng et al|2014}}

The APG system establishes eleven orders of monocots.{{sfn|Cantino et al|2007}}{{sfn|APG IV|2016}} These form three grades, the [[alismatid monocots]], [[lilioid monocots]] and the [[commelinid monocots]] by order of branching, from early to late. In the following [[cladogram]] numbers indicate [[crown group]] (most recent common ancestor of the sampled species of the clade of interest) divergence times in [[mya (unit)|mya]] (million years ago).{{sfn|Hertwick et al.|2015}}

{|
|{{anchor|Clad2}}'''Cladogram 2: The phylogenetic composition of the monocots'''{{sfn|APG IV|2016}}{{sfn|Givnish et al|2018}}

{{barlabel|size=12|at1=5.5|label1=[[Lilioid monocots]] |bar1=purple|at2=2|label2=[[Alismatid monocots]]|bar2=green|style=font-size:100%;line-height:125%;width:400px;|cladogram=

{{clade
|align=center
|label1='''monocots''' (131 [[myr|MYA]])
|1={{clade
    |1={{clade
       |1={{clade
       |label1=
        |1=[[Acorales]]|barbegin1=green
        |2={{clade
           |label1=
           |1=[[Alismatales]]|barend1=green
          |label2=122 MYA
          |2={{clade
            |1=[[Petrosaviales]] | barbegin1=purple
            |label1=
            |2={{clade
              |label1=120 MYA
              |1={{clade
                |1=[[Dioscoreales]] (115 MYA)| bar1=purple
                |2=[[Pandanales]] (91 MYA) | bar2=purple
                 }}
              |2={{clade 
                |1=[[Liliales]] (121 MYA)| bar1=purple
                |label2=121 MYA
                |2={{clade 
                  |1=[[Asparagales]] (120 MYA)| barend1=purple
                  |label2=[[commelinids]] (118 MYA)
                  |2={{clade
                    |label1=
                    |1=[[Arecales]]
                    |2={{clade
                      |label1=
                      |1=[[Poales]]
                      |2={{clade
                        |label1=
                        | 1= [[Zingiberales]]
                        | 2= [[Commelinales]]
                         }}
                       }}
                     }}
                   }}
                 }}
               }}
             }}
           }}
         }}
       }}
     }}
   }}
}}
|}

{{Clear}}
Of some 70,000 [[species]],<ref name=CoL/> by far the largest number (65%) are found in two [[Family (biology)|families]], the orchids and grasses. The orchids ([[Orchidaceae]], [[Asparagales]]) contain about 25,000 species and the grasses ([[Poaceae]], [[Poales]]) about 11,000. Other well known groups within the Poales [[Order (biology)|order]] include the [[Cyperaceae]] (sedges) and [[Juncaceae]] (rushes), and the monocots also include familiar families such as the palms ([[Arecaceae]], Arecales) and lilies ([[Liliaceae]], [[Liliales]]).{{sfn|Fay|2013}}{{sfn|Panis|2008}}