Stylidiaceae
Encyclopedia
The family Stylidiaceae is a taxon of dicotyledonous flowering plant
s. It consists of five genera with over 240 species, most of which are endemic to Australia
and New Zealand
. Members of Stylidiaceae are typically grass-like herbs or small shrubs and can be perennials
or annuals
. Most species are free standing or self-supporting, though a few can be climbing or scrambling (Stylidium scandens
uses leaf tips recurved into hooks to climb).
The pollination mechanisms of Stylidium and Levenhookia
are unique and highly specialized. In Stylidium the floral column
that consists of the fused stamen
and style springs violently from one side (usually under the flower) when triggered, which deposits the pollen on a visiting insect. In Levenhookia, however, the column is immobile, but the hooded labellum
is triggered and sheds pollen.
In 1981, only about 155 species were known in the family. The current number of species by genus (reported in 2002) is as follows: Forstera - 5, Levenhookia - 10, Oreostylidium - 1, Phyllachne - 4, and Stylidium - 221. These numbers, especially for Stylidium, are changing rapidly as new species are described.
is sometimes included in Stylidiaceae in the monogeneric subfamily Donatioideae. The APG II system
recommends its inclusion in Stylidiaceae but allows for the optional recognition of the family Donatiaceae. Molecular and phylogenetic analysis
have determined that Donatia is a sister-group to Stylidiaceae and therefore placing Donatia in its own family has been recommended by several authorities. Including Donatia within the Stylidiaceae would endanger its status as a monophyletic group.
Donatioideae and Stylidioideae were described by Johannes Mildbraed
in his 1908 taxonomic monograph of the family. The subfamilies were created to distinguish the difference between the five typical genera
of the Stylidiaceae from the single genus Donatia
, which Mildbraed placed in Donatioideae. The subfamily taxonomy represents the taxonomic uncertainty of Donatia, which has often been placed in its own family, Donatiaceae, or other families such as the Saxifragaceae
.
Mildbraed's classification also included two tribes
: Phyllachneae, which included the genera Forstera and Phyllachne, and Stylidieae, which included Levenhookia, Oreostylidium, and Stylidium. This level of infraspecific taxonomy is not used in recent research, but the groupings are supported by molecular data that suggest Forstera and Phyllachne are closely related but distinct from the other three.
APG II places Stylidiaceae and Donatiaceae in the Asterales
. The Cronquist system
placed both families in the Campanulales
. The Takhtajan
and Reveal
systems place both families in the order Stylidiales. The Dahlgren system
uses the same Stylidiales order, but it omits Donatiaceae. The Thorne system
shifts Stylidiaceae into the Saxifragales
order.
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
s. It consists of five genera with over 240 species, most of which are endemic to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. Members of Stylidiaceae are typically grass-like herbs or small shrubs and can be perennials
Perennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...
or annuals
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...
. Most species are free standing or self-supporting, though a few can be climbing or scrambling (Stylidium scandens
Stylidium scandens
Stylidium scandens is a dicotyledonous plant that belongs to the genus Stylidium . S. scandens is endemic to Australia and is found primarily in the southwestern region of Western Australia...
uses leaf tips recurved into hooks to climb).
The pollination mechanisms of Stylidium and Levenhookia
Levenhookia
Levenhookia, also known as the styleworts, is a genus of ten recognized species in the family Stylidiaceae and is endemic to Australia. The genus is restricted to Western Australia almost exclusively with a few exceptions: L. pusillas range extends into South Australia, L. dubias range extends...
are unique and highly specialized. In Stylidium the floral column
Column (botany)
The column, or technically the gynostemium, is a reproductive structure that can be found in several plant families: Aristolochiaceae, Orchidaceae, and Stylidiaceae....
that consists of the fused stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
and style springs violently from one side (usually under the flower) when triggered, which deposits the pollen on a visiting insect. In Levenhookia, however, the column is immobile, but the hooded labellum
Labellum
Labellum is the Latin diminutive of labium, meaning lip. These are anatomical terms used descriptively in biology, for example in Entomology and botany.-Botany:...
is triggered and sheds pollen.
In 1981, only about 155 species were known in the family. The current number of species by genus (reported in 2002) is as follows: Forstera - 5, Levenhookia - 10, Oreostylidium - 1, Phyllachne - 4, and Stylidium - 221. These numbers, especially for Stylidium, are changing rapidly as new species are described.
Taxonomy
The genus DonatiaDonatia
Donatia is a genus of two cushion plant species in the monogeneric family Donatiaceae. In the past, Donatia has been placed in the subfamily Donatioideae, described by Johannes Mildbraed in his 1908 taxonomic monograph of the family Stylidiaceae...
is sometimes included in Stylidiaceae in the monogeneric subfamily Donatioideae. The APG II system
APG II system
The APG II system of plant classification is the second, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in April 2003 by the Angiosperm Phylogeny Group. It was a revision of the first APG system, published in 1998, and was superseded in 2009...
recommends its inclusion in Stylidiaceae but allows for the optional recognition of the family Donatiaceae. Molecular and phylogenetic analysis
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
have determined that Donatia is a sister-group to Stylidiaceae and therefore placing Donatia in its own family has been recommended by several authorities. Including Donatia within the Stylidiaceae would endanger its status as a monophyletic group.
Donatioideae and Stylidioideae were described by Johannes Mildbraed
Johannes Mildbraed
Gottfried Wilhelm Johannes Mildbraed was a German botanist that specialized in mosses, ferns, and various spermatophytes. He is well-known for authoring the most current monograph and taxonomic treatment of the family Stylidiaceae in 1908 as part of the unfinished Das Pflanzenreich series. The...
in his 1908 taxonomic monograph of the family. The subfamilies were created to distinguish the difference between the five typical genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of the Stylidiaceae from the single genus Donatia
Donatia
Donatia is a genus of two cushion plant species in the monogeneric family Donatiaceae. In the past, Donatia has been placed in the subfamily Donatioideae, described by Johannes Mildbraed in his 1908 taxonomic monograph of the family Stylidiaceae...
, which Mildbraed placed in Donatioideae. The subfamily taxonomy represents the taxonomic uncertainty of Donatia, which has often been placed in its own family, Donatiaceae, or other families such as the Saxifragaceae
Saxifragaceae
Saxifragaceae is a plant family with about 460 known species in 36 genera. In Europe there are 12 genera.The flowers are hermaphroditic and actinomorphic...
.
Mildbraed's classification also included two tribes
Tribe (biology)
In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...
: Phyllachneae, which included the genera Forstera and Phyllachne, and Stylidieae, which included Levenhookia, Oreostylidium, and Stylidium. This level of infraspecific taxonomy is not used in recent research, but the groupings are supported by molecular data that suggest Forstera and Phyllachne are closely related but distinct from the other three.
APG II places Stylidiaceae and Donatiaceae in the Asterales
Asterales
Asterales is an order of dicotyledonous flowering plants that includes the composite family and its related families.The order is a cosmopolite, and includes mostly herbaceous species, although a small number of trees and shrubs are also present.The Asterales can be characterized on the...
. The Cronquist system
Cronquist system
The Cronquist system is a taxonomic classification system of flowering plants. It was developed by Arthur Cronquist in his texts An Integrated System of Classification of Flowering Plants and The Evolution and Classification of Flowering Plants .Cronquist's system places flowering plants into two...
placed both families in the Campanulales
Campanulales
Campanulales is a valid botanic name for a plant order. It was used in the Cronquist system as an order within the subclass Asteridae in the class Magnoliopsida flowering plants...
. The Takhtajan
Takhtajan system
A system of plant taxonomy, the Takhtajan system of plant classification was published by Armen Takhtajan, in several versions from the 1950s onwards. It is usually compared to the Cronquist system. Key publications:-External links:* Takhtajan system at...
and Reveal
Reveal system
A modern system of plant taxonomy, the Reveal system of plant classification was drawn up by the botanist J.L. Reveal , professor emeritus at the Norton Brown Herbarium, Maryland .The last update of the system was made in 1999...
systems place both families in the order Stylidiales. The Dahlgren system
Dahlgren system
One of the modern systems of plant taxonomy, the Dahlgren system was published by monocot specialist Rolf Dahlgren. His wife Gertrud Dahlgren carried on after his death.According to the extensive listing by Professor Reveal One of the modern systems of plant taxonomy, the Dahlgren system was...
uses the same Stylidiales order, but it omits Donatiaceae. The Thorne system
Thorne system (1992)
A modern system of plant taxonomy, the Thorne system of plant classification was drawn up by the botanist Robert F. Thorne . He replaced it in 2000 with a new system. These two systems were published in:...
shifts Stylidiaceae into the Saxifragales
Saxifragales
Saxifragales is an order of flowering plants. Their closest relatives are a large eudicot group known as the rosids by the definition of rosids given in the APG II classification system. Some authors define the rosids more widely, including Saxifragales as their most basal group. Saxifragales is...
order.