| Huerteales | |
|---|---|
 | |
| Perrottetia sandwicensis | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Clade: | Malvids |
| Order: | Huerteales Doweld[1] |
| Families | |
Huerteales is thebotanical name for anorder offlowering plants.[2] It is one of the 17 orders that make up the largeeudicot group known as therosids in theAPG III system ofplant classification.[1][3] Within the rosids, it is one of the orders inMalvidae,[4] a group formerly known aseurosids II and now known informally as themalvids. This is true whether Malvidae iscircumscribedbroadly to include eight orders as in APG III, or more narrowly to include only four orders.[1] Huerteales consists of four smallfamilies,Petenaeaceae,Gerrardinaceae,Tapisciaceae, andDipentodontaceae.[5]
Petenaeaceae consists of a single genus and speciesPetenaea cordata from Southern Mexico, Guatemala and Belize.[6]
Gerrardinaceae consists of a single genus,Gerrardina.[7] Tapisciaceae has two genera,Tapiscia andHuertea.[8][9]
Until 2006, Dipentodontaceae was treated as consisting of a single genus,Dipentodon.[10] Since that time, some authors have includedPerrottetia in Dipentodontaceae, even though no formal revision of the family has been published as of 2008.[11] Thus the order Huerteales consists of six genera. The largest genus,Perrottetia, contains about 15 of the approximate total of 25species in the order.[12]
The Huerteales areshrubs or smalltrees found in mosttropical or warmtemperate regions. The flowers ofPerrottetia have been studied in detail,[13] but otherwise, all five of the genera are poorly known. The order is based onmolecular phylogenetic analysis ofDNA sequences.
All of the Huerteales arewoody plants. The leaves arealternate withtoothed margins. Theinflorescence iscymose, but sometimes nearlyracemose orumbelliform. The bases of thecalyx,corolla andstamens are fused to form ahypanthium which is in some cases very short. Theovary isunilocular, at least at the top, with one or twoovules percarpel. The number of carpels is variable.
Other characters are generally found in Huerteales, but with the exceptions noted below.Gerrardina differs from the rest of Huerteales in that the stamens are opposite thepetals, instead of being opposite thesepals.Dipentodon andPerrottetia are distinctive in that the calyx and corolla are not well differentiated, but resemble each other.Tapiscia andHuertea have a calyx tube andcompound, rather than simple leaves.Tapiscia has auniloculate ovary with a single ovule.[9]Huertea has one locule containing two ovules, or two locules, each containing one ovule.[8]Gerrardina,Dipentodon, andPerrottetia have two ovules in each locule.Tapiscia lacks thenectary disk that is characteristic of the order.Huertea lacks stipules.
Until the first decade of the twenty-first century, the five genera of Huerteales had usually been placed into three unrelated families.Tapiscia andHuertea had long been known to be related. Most authors had placed them inStaphyleaceae and had placed that family in the orderSapindales.Armen Takhtajan established the family Tapisciaceae in 1987 and placed it in Sapindales, but this treatment was not followed by many others and it did not stand up tophylogenetic analysis. Since that time, Staphyleaceae has beenrecircumscribed. It no longer includesTapiscia andHuertea[14] and it is in the orderCrossosomatales.[15]
For most of the twentieth century,Gerrardina andDipentodon had usually been placed in Flacourtiaceae, a family that is now recognized by only a fewtaxonomists, and then only as asegregate ofSalicaceae.[16][17]Perrottetia, meanwhile, had usually been placed, with considerable doubt, inCelastraceae.[18]
Ever sinceDipentodon was named in 1911, there had been occasional suggestions that it might be related toTapiscia andHuertea.[5] In 2001, Alexander Doweld established the order Huerteales,[19] defining it to consist ofTapiscia,Huertea, andDipentodon.[20] This grouping was later supported bymolecular phylogenetic studies.[5] In 2006, a study ofDNA sequences showed thatPerrottetia was misplaced inCelastrales and that it issister toDipentodon in Huerteales.[18] Also in 2006, it was found thatGerrardina is a malvid, but its placement within this group remained uncertain.[7]
In 2009, Andreas Worberg and co-authors produced the first phylogenetic study that included all of the genera of Huerteales. From one of their data matrices, they derived a well supported phylogeny for the order, as well as strongly supported relationships among the four orders of malvids.[5]
The phylogeny shown below is the one found by Worberg and co-authors.Monospecific genera are represented by species names.
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