Editing Monocotyledon (section)

=== Modern era ===

Over the 1980s, a more general review of the classification of [[angiosperms]] was undertaken. The 1990s saw considerable progress in plant [[phylogenetics]] and [[cladistic]] theory, initially based on ''[[rbcL]]'' gene sequencing and cladistic analysis, enabling a [[phylogenetic tree]] to be constructed for the flowering plants.{{sfn|Chase et al|1993}} The establishment of major new [[clades]] necessitated a departure from the older but widely used classifications such as Cronquist and Thorne, based largely on morphology rather than genetic data. These developments complicated discussions on [[plant evolution]] and necessitated a major taxonomic restructuring.{{sfn|APG|1998}}{{sfn|APG III|2009}}

This [[DNA]] based [[molecular phylogenetic]] research confirmed on the one hand that the monocots remained as a well defined [[monophyly|monophyletic]] group or [[clade]], in contrast to the other historical divisions of the flowering plants, which had to be substantially reorganized.{{sfn|Chase|2004}} No longer could the angiosperms be simply divided into monocotyledons and dicotyledons; it was apparent that the monocotyledons were but one of a relatively large number of defined groups within the angiosperms.{{sfn|Bremer|Wanntorp|1978}} Correlation with morphological criteria showed that the defining feature was not cotyledon number but the separation of angiosperms into two major [[pollen]] types, [[uniaperturate]] ([[monosulcate]] and monosulcate-derived) and triaperturate (tricolpate and tricolpate-derived), with the monocots situated within the uniaperturate groups.{{sfn|Chase et al|1993}} The formal taxonomic ranking of Monoctyledons thus became replaced with monocots as an informal clade.{{sfn|Chase|Stevenson|Wilkin|Rudall|1995b}}{{sfn|Chase|2004}} This is the name that has been most commonly used since the publication of the [[Angiosperm Phylogeny Group]] [[APG system|(APG) system]] in 1998 and regularly updated since.{{sfn|APG|1998}}{{sfn|APG II|2003}}{{sfn|APG III|2009}}{{sfn|LAPGIII|2009}}{{sfn|Chase|Reveal|2009}}{{sfn|APG IV|2016}}

Within the angiosperms, there are two major [[evolutionary grade|grade]]s, a small early branching [[basal (phylogenetics)|basal]] grade, the [[basal angiosperms]] (ANA grade) with three [[lineage (evolution)|lineages]] and a larger late branching grade, the [[core angiosperms]] (mesangiosperms) with five lineages, as shown in the [[cladogram]].

{|
|{{anchor|Clad1}}'''Cladogram I: Phylogenetic position of the monocots within the angiosperms in APG IV (2016)'''{{sfn|APG IV|2016}}
{{barlabel
|size=8
|at1=2|bar1=green|label1=basal angiosperms
|at2=6|bar2=purple|label2=core angiosperms
|cladogram=
{{clade|style=font-size:100%;line-height:100%

|label1=[[angiosperms]]
|1={{clade
  |1=[[Amborellales]]|barbegin1=green
  |2={{clade
    |1=[[Nymphaeales]]|bar1=green
    |2={{clade
      |1=[[Austrobaileyales]]|barend1=green
      |label2=
      |2={{clade
        |1={{clade
          |1=[[magnoliids]]|barbegin1=purple
          |2=[[Chloranthales]]|bar2=purple
           }}
        |2={{clade
          |1='''monocots'''|bar1=purple
          |2={{clade
            |1=[[Ceratophyllales]]|bar1=purple
            |2=[[eudicots]]|barend2=purple
             }}
           }}
         }}
       }}
     }}
   }}
}}
}}
|}