View source for Buxales

{{short description|Order of eudicot flowering plants}}
{{Automatic taxobox
| taxon = Buxales
| image = Illustration_Buxus_sempervirens0.jpg
| image_caption = ''[[Buxus sempervirens]]''
| authority = [[Armen Takhtajan|Takht.]] ex [[James L. Reveal|Reveal]]<ref name=APG3/>
| subdivision_ranks = Families
| subdivision =
*[[Buxaceae]] {{au|Dumort., nom. cons.}}
*[[Didymelaceae]] {{au|Leandri}} (may be included in Buxaceae; see text)
*[[Haptanthaceae]] {{au|C.Nelson}} (may be included in Buxaceae; see text)
}}

The '''Buxales''' are a small order of [[eudicot]] [[flowering plant]]s, recognized by the [[APG IV system]] of 2016. The order includes the family [[Buxaceae]]; the families [[Didymelaceae]] and [[Haptanthaceae]] may also be recognized or may be included in the Buxaceae. Many members of the order are evergreen shrubs or trees, although some are herbaceous perennials. They have separate "male" (staminate) and "female" (carpellate) flowers, mostly on the same plant (i.e. they are mostly [[Monoecy|monoecious]]). Some species are of economic importance either for the wood they produce or as [[ornamental plant]]s.

==Description==

The Buxales have relatively few obvious shared features distinguishing them from related groups of plants (i.e. few obvious [[Synapomorphy|synapomorphies]]). One is the presence of a particular type of [[alkaloid]] or pseudoalkaloid, [[Pregnane|pregnane steroids]]. They have unisexual flowers (i.e. separate staminate or "male" flowers and carpellate or "female" flowers), most being [[Monoecy|monoecious]]. The flowers are small, less than 7&nbsp;mm across. The [[tepal]]s have a single [[vascular bundle]] (trace). Other characters common to the order include leaves with entire (untoothed) margins, flowers arranged in [[raceme]]s, small [[Stigma (botany)|style]]s capable of receiving pollen along their entire length rather than having a separate stigma, one to two [[ovule]]s per [[carpel]], and seeds with [[Seed#Seed coat|testae]] (coats) made up of several cell layers.<ref name=APweb/>

''[[Didymeles]]'', the sole genus in the family [[Didymelaceae]], consists of two species of evergreen tree occurring only in [[Madagascar]]. It is dioecious, i.e. with staminate and carpellate flowers on separate plants. [[Buxaceae]] (including [[Haptanthaceae]]) is more diverse, with five or six genera totalling about 115 species, and is found in most temperate and tropical areas of the world. Most species are evergreen shrubs or small trees, but some (such as those of ''[[Pachysandra]]'') are herbaceous perennials.<ref name=APweb/>

==Taxonomy==

In the [[APG III system]] of 2009, the order includes two families, [[Buxaceae]] and [[Haptanthaceae]]. Unlike previous classifications (including the [[APG II system]] of 2003), APG III does not recognize the family [[Didymelaceae]], but includes the genus ''[[Didymeles]]'' in Buxaceae.<ref name=APG3/> Subsequent research published in 2011 suggests that the Haptanthaceae are embedded in the Buxaceae, possibly as the sister to ''[[Buxus]]'',<ref name=ShipShip11/> and {{as of|2014|September|lc=yes}} the [[Angiosperm Phylogeny Website]] no longer recognizes Haptanthaceae.<ref name=APweb/> In the 2016 [[APG IV system]], Haptanthaceae is incorporated into Buxaceae, which leaves Buxaceae the only family under ''Buxales''.<ref name=APG4/>

===Phylogeny===

The Buxales are placed within the [[eudicots]] but outside the [[core eudicots]], in a paraphyletic group of basal eudicots. The [[monophyly]] of the order and its general position relative to other eudicots has been confirmed by many studies.<ref name=APweb/> One possible phylogenetic tree is shown below, where the precise ordering of the basal eudicots is still uncertain.<ref name=APweb/>

{{barlabel
|size=5
|at1=2.5|bar1=green|label1=basal eudicots
|cladogram=
{{clade
|label1=[[eudicots]]
|1={{clade
   |1=[[Ranunculales]]|barbegin1=green
   |2={{clade
      |1=[[Proteales]] and [[Sabiales]]|bar1=green
      |2={{clade
         |1=[[Trochodendrales]]|bar1=green
         |2={{clade
            |1='''Buxales'''|barend1=green
            |2=core eudicots
            }}
         }}
      }}
   }}
}}
}}

One difference between the basal eudicots and the core eudicots is that the latter appear to have undergone a complete triplication of the nuclear genome which is absent in the former.<ref name=APweb_Ce/> Molecular phylogenetic studies have produced slightly different internal arrangements of the families and genera within the order;<ref name=ShipShip11/> hence the variation in the number of families into which it is divided.

===Genera===
[[File:Frühblühender Bodendecker.JPG|thumb|''[[Pachysandra terminalis]]'']]
Didymelaceae<ref name=APweb/> or Buxaceae<ref name=APG3/>
* ''[[Didymeles]]'' <small>Thouars</small>
Buxaceae
* ''[[Buxus]]'' <small>L.</small> (including ''Notobuxus'' <small>Oliver</small>)
* ''[[Pachysandra]]'' <small>Michx.</small>
* ''[[Sarcococca]]'' <small>Lindl.</small>
* ''[[Styloceras]]'' <small>Kunth ex A.Juss.</small>
Buxaceae<ref name=APweb/> or Haptanthaceae<ref name=APG3/>
* ''[[Haptanthus]]'' <small>Goldberg & C.Nelson</small>

===Former treatment===

In the [[Cronquist system]] of 1981, the Buxaceae were associated with the [[Euphorbiaceae]] s.l.,<ref name=APweb/> and the Didymelaceae were given their own order. In the [[APG II system]] of 2003, the [[Buxaceae]] were a family unplaced as to order in the [[eudicots]], optionally including the genus ''[[Didymeles]]'', which could alternatively be placed in its own family.<ref name=APG2/>

===Age===

According to [[molecular clock]] calculations, the lineage that led to Buxales split from other plants about 129 [[million years ago]]<ref>{{cite journal |last1= Magallon |first1= S |last2= Gomez-Acevedo |first2= S |last3= Sanchez-Reyes |first3= LL |last4= Tania Hernandez-Hernandez |first4= T |title = A metacalibrated time-tree documents the early rise of flowering plant phylogenetic diversity |journal= New Phytologist |date= 2015 | volume = 207 |issue= 2 |pages= 437–453 | doi = 10.1111/nph.13264|pmid= 25615647 |bibcode= 2015NewPh.207..437M }}</ref> or 120 million years ago.<ref>{{cite journal|last1=Zeng|first1=Liping|last2=Zhang|first2=Qiang|last3=Sun|first3=Renran|last4=Kong|first4=Hongzhi|last5=Zhang|first5=Ning|last6=Ma|first6=Hong|title=Resolution of deep angiosperm phylogeny using conserved nuclear genes and estimates of early divergence times|journal=[[Nature Communications]]|date=24 September 2014|volume=5|issue=4956|pages=4956|doi=10.1038/ncomms5956|pmid=25249442|ref={{harvid|Zeng et al|2014}}|pmc=4200517|bibcode=2014NatCo...5.4956Z}}</ref>

==Uses==

Some species of the Buxaceae are of economic importance. ''[[Buxus sempervirens]]'' (common box) and ''[[Buxus macowanii]]'' (Cape box) produce hard wood valued for carving and engraving. Species are also used as ornamental garden plants and for [[bonsai]]. Common box is used for hedging and border edging. Species of ''[[Pachysandra]]'' are used as ground cover. Species of ''[[Sarcococca]]'' produce small but strongly scented flowers in the winter.<ref name=Chan78/>

==References==
{{Reflist|refs=
<ref name=APG2>{{Citation |last=Angiosperm Phylogeny Group II |year=2003 |title=An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II |journal=Botanical Journal of the Linnean Society |volume=141 |issue=4 |pages=399–436 |doi=10.1046/j.1095-8339.2003.t01-1-00158.x |doi-access= }}</ref>

<ref name=APG3>{{Citation |last=Angiosperm Phylogeny Group |year=2009 |title=An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III |journal=Botanical Journal of the Linnean Society |volume=161 |issue=2 |pages=105–121 |doi=10.1111/j.1095-8339.2009.00996.x |doi-access=free |hdl=10654/18083 |hdl-access=free }}</ref>

<ref name="APG4">{{Cite journal |last=Angiosperm Phylogeny Group |year=2016 |title=An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV |journal=Botanical Journal of the Linnean Society |volume=181 |issue=1 |pages=1–20 |doi=10.1111/boj.12385 |doi-access=free }}</ref>

<ref name=APweb>{{Citation |last=Stevens |first=P.F.  |title=Buxales |work=Angiosperm Phylogeny Website |url=http://www.mobot.org/MOBOT/Research/APweb/orders/buxalesweb.htm#Buxales |access-date=2014-09-25 }}</ref>

<ref name=APweb_Ce>{{Citation |last=Stevens |first=P.F. |date=2001{{ndash}}2012 |title=Core eudicots / Gunneridae |work=Angiosperm Phylogeny Website |url=http://www.mobot.org/MOBOT/Research/APweb/orders/gunneralesweb.htm#Guncor |access-date=2014-09-26 }}</ref>

<ref name=Chan78>{{Citation |last1=Chant |first1=S.R. |year=1978 |editor-last=Heywood |editor-first=V.H. |editor2-last=Moore |editor2-first=D.M. |editor3-last=Richardson |editor3-first=I.B.K. |editor4-last=Stearn |editor4-first=W.T. |contribution=Buxaceae |title=Flowering Plants of the World |pages=[https://archive.org/details/floweringplantso0000unse/page/183 183–5] |location=Oxford, etc. |publisher=Oxford University Press |name-list-style=amp |isbn=9780195210378 |url-access=registration |url=https://archive.org/details/floweringplantso0000unse/page/183 }}</ref>

<ref name=ShipShip11>{{Citation |last1=Shipunov |first1=A.B. |last2=Shipunova |first2=E. |date=2011 |title=''Haptanthus'' story: Rediscovery of enigmatic flowering plant from Honduras |journal=American Journal of Botany |volume=98 |issue=4 |pages=761–763 |doi=10.3732/ajb.1000307 |pmid=21613172|bibcode=2011AmJB...98..761S }}</ref>
}}

{{Angiosperm orders}}
{{Taxonbar|from=Q21020}}

[[Category:Monotypic angiosperm orders]]
[[Category:Eudicots]]