Huerteales
Encyclopedia
Huerteales is the botanical name
for an order
of flowering plants. It is one of the 17 orders that make up the large eudicot group known as the rosids
in the APG III system
of plant classification
. Within the rosids, it is one of the orders in Malvidae, a group formerly known as eurosids II and now known informally as the malvids. This is true whether Malvidae is circumscribed
broadly to include eight orders as in APG III, or more narrowly to include only four orders. Huerteales consists of three small families
, Petenaeaceae, Gerrardinaceae, Tapisciaceae
, and Dipentodontaceae
.
Petenaeaceae consists of a singe genus and species Petenaea
cordata from Southern Mexico, Guatemala and Belize .
Gerrardinaceae consists of a single genus, Gerrardina
. Tapisciaceae has two genera, Tapiscia
and Huertea
. Until 2006, Dipentodontaceae was treated as consisting of a single genus, Dipentodon. Since that time, some authors have included Perrottetia in Dipentodontaceae, even though no formal revision of the family has been published as of 2008. Thus the order Huerteales consists of five genera. The largest genus, Perrottetia, contains about 15 of the approximate total of 25 species
in the order.
The Huerteales are shrub
s or small tree
s found in most tropical
or warm temperate regions. The flowers of Perrottetia have been studied in detail, but otherwise, all five of the genera are poorly known. Their true relationships have been found only in the twenty-first century with molecular phylogenetic analysis of DNA sequence
s.
s. The leaves are alternate with toothed
margins. The inflorescence
is cymose, but sometimes nearly racemose
or umbelliform
. The bases of the calyx, corolla and stamen
s are fused to form a hypanthium
which is in some cases very short. The ovary
is unilocular
, at least at the top, with one or two ovule
s per carpel
. 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 the petal
s, instead of being opposite the sepals. Dipentodon and Perrottetia are distinctive in that the calyx and corolla are not well differentiated, but resemble each other. Tapiscia and Huertea have a calyx tube and compound, rather than simple leaves. Tapiscia has a uniloculate
ovary with a single ovule. Huertea has one locule containing two ovules, or two locules, each containing one ovule. Gerrardina, Dipentodon, and Perrottetia have two ovules in each locule. Tapiscia lacks the nectary disk that is characteristic of the order. Huertea lacks stipules.
and had placed that family in the order Sapindales
. 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 to phylogenetic analysis. Since that time, Staphyleaceae has been recircumscribed
. It no longer includes Tapiscia and Huertea and it is in the order Crossosomatales
.
For most of the twentieth century, Gerrardina and Dipentodon had usually been placed in Flacourtiaceae, a family that is now recognized by only a few taxonomists
, and then only as a segregate
of Salicaceae
. Perrottetia, meanwhile, had usually been placed, with considerable doubt, in Celastraceae
.
Ever since Dipentodon was named in 1911, there had been occasional suggestions that it might be related to Tapiscia and Huertea. In 2001, Alexander Doweld established the order Huerteales, defining it to consist of Tapiscia, Huertea, and Dipentodon. This grouping was later supported by molecular phylogenetic studies. In 2006, a study of DNA sequence
s showed that Perrottetia was misplaced in Celastrales
and that it is sister to Dipentodon in Huerteales. Also in 2006, it was found that Gerrardina is a malvid, but its placement within this group remained uncertain.
In 2009, Andreas Worberg and co-authors produced the first phylogenetic study that included all of the genera of Huerteales. From one of their datasets, they derived a well supported phylogeny for the order, as well as strongly supported relationships among the four orders of malvids.
Botanical name
A botanical name is a formal scientific name conforming to the International Code of Botanical Nomenclature and, if it concerns a plant cultigen, the additional cultivar and/or Group epithets must conform to the International Code of Nomenclature for Cultivated Plants...
for an order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of flowering plants. It is one of the 17 orders that make up the large eudicot group known as the rosids
Rosids
The rosids are members of a large clade of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms. The clade is divided into 16 to 20 orders, depending upon circumscription and classification. These orders, in turn, together comprise about 140 families...
in the APG III system
APG III system
The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy...
of plant classification
History of plant systematics
The history of plant systematics—the biological classification of plants—stretches from the work of ancient Greek to modern evolutionary biologists. As a field of science, plant systematics came into being only slowly, early plant lore usually being treated as part of the study of...
. Within the rosids, it is one of the orders in Malvidae, a group formerly known as eurosids II and now known informally as the malvids. This is true whether Malvidae is circumscribed
Circumscription (taxonomy)
In taxonomy, circumscription is the definition of the limits of a taxonomic group of organisms. One goal of taxonomy is to achieve a stable circumscription for every taxonomic group. Achieving stability can be simple or difficult....
broadly to include eight orders as in APG III, or more narrowly to include only four orders. Huerteales consists of three small families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
, Petenaeaceae, Gerrardinaceae, Tapisciaceae
Tapisciaceae
Tapisciaceae is the botanical name for a family of flowering plants. Until recently it had been abandoned by taxonomists, and it was not recognised in the APG II system of 2003. Recently, however, it has been reinstated to encompass the two small genera Tapiscia and Huertea....
, and Dipentodontaceae
Dipentodontaceae
Dipentodon is a genus of flowering plants in the family Dipentodontaceae. Its only species, Dipentodon sinicus, is a small, deciduous tree native to southern China, Burma, and northern India. It has been little studied and until recently its affinities remained obscure.- Description :Dipentodon...
.
Petenaeaceae consists of a singe genus and species Petenaea
Petenaea
Petenaea cordata was first described in Elaeocarpaceae and later placed in Tiliaceae, but most authors have been uncertain about its familial affinities. It was considered a taxon incertae sedis in the Angiosperm Phylogeny Group classification...
cordata from Southern Mexico, Guatemala and Belize .
Gerrardinaceae consists of a single genus, Gerrardina
Gerrardina
Gerrardina is a genus of two species of scrambling shrub found in eastern Africa. It is placed alone in family Gerrardiaceae. Placement are ordinal level is problematic; currently it is placed tentatively in Huerteales.-References:...
. Tapisciaceae has two genera, Tapiscia
Tapiscia
Tapiscia is a genus of flowering plants in the family Tapisciaceae. Some authors recognize only one species, Tapiscia sinensis. Other authors recognize two species, T. sinensis and T. yunnanensis....
and Huertea
Huertea
Huertea is a genus of plant in family Staphyleaceae. It contains the following species :* Huertea cubensis, Griseb....
. Until 2006, Dipentodontaceae was treated as consisting of a single genus, Dipentodon. Since that time, some authors have included Perrottetia in Dipentodontaceae, even though no formal revision of the family has been published as of 2008. Thus the order Huerteales consists of five genera. The largest genus, Perrottetia, contains about 15 of the approximate total of 25 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in the order.
The Huerteales are shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
s or small tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s found in most tropical
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
or warm temperate regions. The flowers of Perrottetia have been studied in detail, but otherwise, all five of the genera are poorly known. Their true relationships have been found only in the twenty-first century with molecular phylogenetic analysis of DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
s.
Description
All of the Huerteales are woody plantWoody plant
A woody plant is a plant that uses wood as its structural tissue. These are typically perennial plants whose stems and larger roots are reinforced with wood produced adjacent to the vascular tissues. The main stem, larger branches, and roots of these plants are usually covered by a layer of...
s. The leaves are alternate with toothed
Leaf shape
In botany, leaf shape is characterised with the following terms :* Acicular : Slender and pointed, needle-like* Acuminate : Tapering to a long point...
margins. The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
is cymose, but sometimes nearly racemose
Raceme
A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...
or umbelliform
Umbel
An umbel is an inflorescence which consists of a number of short flower stalks which are equal in length and spread from a common point, somewhat like umbrella ribs....
. The bases of the calyx, corolla and stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s are fused to form a hypanthium
Hypanthium
A hypanthium is a floral structure consisting of the bases of the sepals, petals, and stamens fused together. Its presence is diagnostic of many families, including the Rosaceae, Grossulariaceae, and Fabaceae...
which is in some cases very short. The ovary
Ovary (plants)
In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...
is unilocular
Locule
A locule is a small cavity or compartment within an organ or part of an organism ....
, at least at the top, with one or two ovule
Ovule
Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center...
s per carpel
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
. 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 the petal
Petal
Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...
s, instead of being opposite the sepals. Dipentodon and Perrottetia are distinctive in that the calyx and corolla are not well differentiated, but resemble each other. Tapiscia and Huertea have a calyx tube and compound, rather than simple leaves. Tapiscia has a uniloculate
Locule
A locule is a small cavity or compartment within an organ or part of an organism ....
ovary with a single ovule. Huertea has one locule containing two ovules, or two locules, each containing one ovule. Gerrardina, Dipentodon, and Perrottetia have two ovules in each locule. Tapiscia lacks the nectary disk that is characteristic of the order. Huertea lacks stipules.
History
Until the first decade of the twenty-first century, the five genera of Huerteales had usually been placed into three unrelated families. Tapiscia and Huertea had long been known to be related. Most authors had placed them in StaphyleaceaeStaphyleaceae
Staphyleaceae is a small family of five genera of flowering plants in the order Crossosomatales, native to the Northern Hemisphere and also in South America. The genus Staphylea, which gives the family its name, contains the "bladdernut" trees.Genera...
and had placed that family in the order Sapindales
Sapindales
Sapindales is a botanical name for an order of flowering plants. Well-known members of Sapindales include citrus; maples, horse-chestnuts, lychees and rambutans; mangos and cashews; frankincense and myrrh; mahogany and neem....
. Armen Takhtajan
Armen Takhtajan
Armen Leonovich Takhtajan or Takhtajian , was a Soviet-Armenian botanist, one of the most important figures in 20th century plant evolution and systematics and biogeography. His other interests included morphology of flowering plants, paleobotany, and the flora of the Caucasus...
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 to phylogenetic analysis. Since that time, Staphyleaceae has been recircumscribed
Circumscription (taxonomy)
In taxonomy, circumscription is the definition of the limits of a taxonomic group of organisms. One goal of taxonomy is to achieve a stable circumscription for every taxonomic group. Achieving stability can be simple or difficult....
. It no longer includes Tapiscia and Huertea and it is in the order Crossosomatales
Crossosomatales
The Crossosomatales are an order, newly recognized by the AGP II, of flowering plants, included within the Rosids, which are part of the eudicots...
.
For most of the twentieth century, Gerrardina and Dipentodon had usually been placed in Flacourtiaceae, a family that is now recognized by only a few taxonomists
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
, and then only as a segregate
Segregate (taxonomy)
In taxonomy, a segregate, or a segregate taxon is created when a taxon is split off, from another taxon. This other taxon will be better known, usually bigger, and will continue to exist, even after the segregate taxon has been split off...
of Salicaceae
Salicaceae
Salicaceae are a family of flowering plants. Recent genetic studies summarized by the Angiosperm Phylogeny Group has greatly expanded the circumscription of the family to contain 55 genera....
. Perrottetia, meanwhile, had usually been placed, with considerable doubt, in Celastraceae
Celastraceae
The Celastraceae , is a family of about 90-100 genera and 1,300 species of vines, shrubs and small trees, belonging to the order Celastrales...
.
Ever since Dipentodon was named in 1911, there had been occasional suggestions that it might be related to Tapiscia and Huertea. In 2001, Alexander Doweld established the order Huerteales, defining it to consist of Tapiscia, Huertea, and Dipentodon. This grouping was later supported by molecular phylogenetic studies. In 2006, a study of DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
s showed that Perrottetia was misplaced in Celastrales
Celastrales
Celastrales is an order of flowering plants. They are found throughout the tropics and subtropics, with only a few species extending far into the temperate regions. There are about 1200 to 1350 species in about 100 genera. All but 7 of these genera are in the large family Celastraceae...
and that it is sister to Dipentodon in Huerteales. Also in 2006, it was found that Gerrardina is a malvid, but its placement within this group remained uncertain.
In 2009, Andreas Worberg and co-authors produced the first phylogenetic study that included all of the genera of Huerteales. From one of their datasets, they derived a well supported phylogeny for the order, as well as strongly supported relationships among the four orders of malvids.