Oreostylidium
Encyclopedia
Oreostylidium is a genus
of flowering plants in the family Stylidiaceae
with a single species, Oreostylidium subulatum, that is endemic
to New Zealand
. O. subulatum is a very small plant with small, white flowers. It has a complicated botanical history that has led to a few proposals to move Oreostylidium to the related genus Stylidium. The researchers cite molecular data and suspect that this species is an extreme example of floral paedomorphosis. This would not be an unprecedented move since the single species was initially described as Stylidium subulatum in 1864 and later moved to its own genus by Sven Berggren
in 1878. It possesses the same kind of glandular trichome
s underneath the flower that make Stylidium species carnivorous plant
s, but it has not yet been tested for the presence of digestive enzymes.
close to the ground. The leaves are glabrous with entire margins
. The scape
, arising from the rosette of leaves, is slender, erect, and about 2 cm tall. The scape, like most species in the related genus Stylidium is covered with glandular trichome
s. Each scape produces a single flower. The calyx
is erect, stout, and very broad (nearly as broad as the ovary
). The ovary is large, oblong, sub-cylindrical, tapering and jointed on to scape.
The flower corolla consists of solitary actinomorphic, white flowers with five petal
s that most resemble the flowers of Forstera
and Phyllachne
(both also in Stylidiaceae). Like all Stylidium species, O. subulatum also possesses a column
, which is the fused stamen
s and stigma. But unlike Stylidium species, it is insensitive or non-mobile and does not move in response to physical stimuli. It has been suggested that Oreostylidium be merged into the genus Stylidium, but the morphological characteristics of the two genera are dissimilar. Researchers have suggested that the floral form O. subulatum had developed by an extreme example of paedomorphosis or reduction. This process may have begun as a result of O. subulatum' s isolation on the islands of New Zealand
. Researchers believe that this species has its origins in Australia
and was established in New Zealand by a very small population and perhaps from a single seed. Faced with survival in a new environment and possessing a flower designed for specific Australian pollinators, the species underwent rapid changes to its morphology. The hypothesis presented in these studies suggests this is how O. subulatum evolved from a common ancestry lineage with Stylidium graminifolium
into the pollinator-generalist it is today. There is also a shift from the Stylidium-like flower designed for cross-pollination to obligate autogamous
pollination. This allowed the plant to perform sexual reproduction in its morphologically immature state because the complicated Stylidium-like flowers were not required for pollination.
and subalpine
regions of New Zealand, but the range is not as extensive as the other Stylidiaceae genera found in New Zealand. Good (1925) in a review of the geographical distribution of Stylidiaceae noted that O. subulatum is confined to the South Island
, though earlier reports place some specimens near Mount Ruapehu
on the North Island
. On the South Island, it was reported as existing at Swampy Hill near Dunedin
and The Grampians near Nelson, New Zealand
.
in 1864 as Stylidium subulatum in the related genus Stylidium. Hooker based his classification on imperfect floral specimens and thus had to rely upon fruit
morphology
and habitat similarities. Working from the fruit morphology alone, Hooker noticed his specimen resembled several members of Stylidium subgenus
Tolypangium. In 1878, Ferdinand von Mueller
proposed that what was known then as Stylidium subulatum be included within the related genus Phyllachne
based on flower morphology. In the same year, Sven Berggren
proposed the move that created the most accepted classification within the genus he created, Oreostylidium.
Then in 1887, William Colenso
described what he thought was a new species, Oreostylidium affine, based on specific morphological differences from previous descriptions of O. subulatum. He noted that he was rather unsure of the specific classification of this new species:
Colenso also admitted in his description of O. affine that the location data for both O. affine and O. subulatum were very similar and at least one morphological detail of his plant specimens was damaged, which could have effected his analysis. O. affine was later placed under O. subulatum as a synonym.
Oreostylidium remained relatively untouched after that until an extensive review of the morphological details of Stylidiaceae was combined with genetic analysis of the chloroplast
DNA
genes rbcL and ndhF in 1998. The result of this study revealed that all major cladistic
trees generated from the data suggested that the genus Oreostylidium is nested within the genus Stylidium. Based on that data, the authors of that study proposed that O. subulatum be known once again under its very first name, Stylidium subulatum and Oreostylidium should be reduced to synonymy of Stylidium. In 2002, another study based on molecular evidence determined that in the most parsimonious cladistic tree, Stylidium graminifolium
and O. subulatum were closely related, with O. subulatum again nested within Stylidium. Based on molecular clock
calculations and their data, the researchers concluded that S. graminifolium and O. subulatum shared a common ancestor about 3 million years ago. The researchers responsible for the 2002 study also concluded that Oreostylidium should be transferred to Stylidium and O. subulatum should retake its former name as Stylidium subulatum.
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 flowering plants in the family Stylidiaceae
Stylidiaceae
The family Stylidiaceae is a taxon of dicotyledonous flowering plants. 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...
with a single species, Oreostylidium subulatum, that is endemic
Endemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to 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...
. O. subulatum is a very small plant with small, white flowers. It has a complicated botanical history that has led to a few proposals to move Oreostylidium to the related genus Stylidium. The researchers cite molecular data and suspect that this species is an extreme example of floral paedomorphosis. This would not be an unprecedented move since the single species was initially described as Stylidium subulatum in 1864 and later moved to its own genus by Sven Berggren
Sven Berggren
Sven Berggren was a Swedish botanist, explorer and university professor. He was a professor at Lund University 1883-1902, later at Uppsala University. He was elected a member of the Royal Swedish Academy of Sciences in 1880....
in 1878. It possesses the same kind of glandular trichome
Trichome
Trichomes are fine outgrowths or appendages on plants and certain protists. These are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae.- Algal trichomes :...
s underneath the flower that make Stylidium species carnivorous plant
Carnivorous plant
Carnivorous plants are plants that derive some or most of their nutrients from trapping and consuming animals or protozoans, typically insects and other arthropods. Carnivorous plants appear adapted to grow in places where the soil is thin or poor in nutrients, especially nitrogen, such as acidic...
s, but it has not yet been tested for the presence of digestive enzymes.
Characteristics
O. subulatum is a very small, cæspitose, and densely tufted plant about 2-3 cm tall. The 2 cm long linear-subulate leaves form a basal rosetteRosette (botany)
In botany, a rosette is a circular arrangement of leaves, with all the leaves at a single height.Though rosettes usually sit near the soil, their structure is an example of a modified stem.-Function:...
close to the ground. The leaves are glabrous with entire margins
Leaf shape
In botany, leaf shape is characterised with the following terms :* Acicular : Slender and pointed, needle-like* Acuminate : Tapering to a long point...
. The scape
Scape (botany)
In botany, scapes are leafless flowering stems that rise from the ground. Scapes can have a single flower or many flowers, depending on the species....
, arising from the rosette of leaves, is slender, erect, and about 2 cm tall. The scape, like most species in the related genus Stylidium is covered with glandular trichome
Trichome
Trichomes are fine outgrowths or appendages on plants and certain protists. These are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae.- Algal trichomes :...
s. Each scape produces a single flower. The calyx
Sepal
A sepal is a part of the flower of angiosperms . Collectively the sepals form the calyx, which is the outermost whorl of parts that form a flower. Usually green, sepals have the typical function of protecting the petals when the flower is in bud...
is erect, stout, and very broad (nearly as broad as 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...
). The ovary is large, oblong, sub-cylindrical, tapering and jointed on to scape.
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 that most resemble the flowers of Forstera
Forstera
Forstera is a genus of small perennial plants in the Stylidiaceae family named in honour of the German naturalists Johann Reinhold Forster and his son, Georg Forster, who had previously described Forsteras sister genus, Phyllachne just five years earlier. It comprises five species that are endemic...
and Phyllachne
Phyllachne
Phyllachne is a genus of four cushion plant species in the family Stylidiaceae. Of the four species, two are endemic to New Zealand, while P. colensoi is also native to Tasmania and P. uliginosa is entirely endemic to southern South America and is the only species in the Stylidiaceae...
(both also in Stylidiaceae). Like all Stylidium species, O. subulatum also possesses a 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....
, which is the fused stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s and stigma. But unlike Stylidium species, it is insensitive or non-mobile and does not move in response to physical stimuli. It has been suggested that Oreostylidium be merged into the genus Stylidium, but the morphological characteristics of the two genera are dissimilar. Researchers have suggested that the floral form O. subulatum had developed by an extreme example of paedomorphosis or reduction. This process may have begun as a result of O. subulatum
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...
. Researchers believe that this species has its origins in 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 was established in New Zealand by a very small population and perhaps from a single seed. Faced with survival in a new environment and possessing a flower designed for specific Australian pollinators, the species underwent rapid changes to its morphology. The hypothesis presented in these studies suggests this is how O. subulatum evolved from a common ancestry lineage with Stylidium graminifolium
Stylidium graminifolium
Stylidium graminifolium, the grass triggerplant, is a dicotyledonous plant that belongs to the genus Stylidium . This species used to belong to the Stylidium graminifolium complex, but the name was conserved for this single species when two others were split from the complex and introduced as new...
into the pollinator-generalist it is today. There is also a shift from the Stylidium-like flower designed for cross-pollination to obligate autogamous
Biological reproduction
Reproduction is the biological process by which new "offspring" individual organisms are produced from their "parents". Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction...
pollination. This allowed the plant to perform sexual reproduction in its morphologically immature state because the complicated Stylidium-like flowers were not required for pollination.
Distribution
O. subulatum is endemic to montaneMontane
In biogeography, montane is the highland area located below the subalpine zone. Montane regions generally have cooler temperatures and often have higher rainfall than the adjacent lowland regions, and are frequently home to distinct communities of plants and animals.The term "montane" means "of the...
and subalpine
Subalpine
The subalpine zone is the biotic zone immediately below tree line around the world. Species that occur in this zone depend on the location of the zone on the Earth, for example, Snow Gum in Australia, or Subalpine Larch, Mountain Hemlock and Subalpine Fir in western North America.Trees in the...
regions of New Zealand, but the range is not as extensive as the other Stylidiaceae genera found in New Zealand. Good (1925) in a review of the geographical distribution of Stylidiaceae noted that O. subulatum is confined to the South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
, though earlier reports place some specimens near Mount Ruapehu
Mount Ruapehu
Mount Ruapehu, or just Ruapehu, is an active stratovolcano at the southern end of the Taupo Volcanic Zone in New Zealand. It is 23 kilometres northeast of Ohakune and 40 kilometres southwest of the southern shore of Lake Taupo, within Tongariro National Park...
on the North Island
North Island
The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
. On the South Island, it was reported as existing at Swampy Hill near Dunedin
Dunedin
Dunedin is the second-largest city in the South Island of New Zealand, and the principal city of the Otago Region. It is considered to be one of the four main urban centres of New Zealand for historic, cultural, and geographic reasons. Dunedin was the largest city by territorial land area until...
and The Grampians near Nelson, New Zealand
Nelson, New Zealand
Nelson is a city on the eastern shores of Tasman Bay, and is the economic and cultural centre of the Nelson-Tasman region. Established in 1841, it is the second oldest settled city in New Zealand and the oldest in the South Island....
.
Botanical history and taxonomy
O. subulatum was originally described by Sir William Jackson HookerWilliam Jackson Hooker
Sir William Jackson Hooker, FRS was an English systematic botanist and organiser. He held the post of Regius Professor of Botany at Glasgow University, and was the first Director of the Royal Botanic Gardens, Kew. He enjoyed the friendship and support of Sir Joseph Banks for his exploring,...
in 1864 as Stylidium subulatum in the related genus Stylidium. Hooker based his classification on imperfect floral specimens and thus had to rely upon fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
and habitat similarities. Working from the fruit morphology alone, Hooker noticed his specimen resembled several members of Stylidium subgenus
Subgenus
In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...
Tolypangium. In 1878, Ferdinand von Mueller
Ferdinand von Mueller
Baron Sir Ferdinand Jacob Heinrich von Mueller, KCMG was a German-Australian physician, geographer, and most notably, a botanist.-Early life:...
proposed that what was known then as Stylidium subulatum be included within the related genus Phyllachne
Phyllachne
Phyllachne is a genus of four cushion plant species in the family Stylidiaceae. Of the four species, two are endemic to New Zealand, while P. colensoi is also native to Tasmania and P. uliginosa is entirely endemic to southern South America and is the only species in the Stylidiaceae...
based on flower morphology. In the same year, Sven Berggren
Sven Berggren
Sven Berggren was a Swedish botanist, explorer and university professor. He was a professor at Lund University 1883-1902, later at Uppsala University. He was elected a member of the Royal Swedish Academy of Sciences in 1880....
proposed the move that created the most accepted classification within the genus he created, Oreostylidium.
Then in 1887, William Colenso
William Colenso
William Colenso was a Cornish Christian missionary to New Zealand, and also a printer, botanist, explorer and politician.-Life:Born in Penzance, Cornwall, he was the cousin of John William Colenso, Bishop of Natal...
described what he thought was a new species, Oreostylidium affine, based on specific morphological differences from previous descriptions of O. subulatum. He noted that he was rather unsure of the specific classification of this new species:
- "This plant resembles Oreostylidium subulatum, Berggren, as carefully drawn by him; (which is also the "Stylidium? subulatum, n. sp.," of Hook. f., as given by him with doubt, from his imperfect specimens, in the "Handbook N.Z. Flora," p. 168;) and it would be by me referred to that species were it not for its differential characters."
Colenso also admitted in his description of O. affine that the location data for both O. affine and O. subulatum were very similar and at least one morphological detail of his plant specimens was damaged, which could have effected his analysis. O. affine was later placed under O. subulatum as a synonym.
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
genes rbcL and ndhF in 1998. The result of this study revealed that all major cladistic
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
trees generated from the data suggested that the genus Oreostylidium is nested within the genus Stylidium. Based on that data, the authors of that study proposed that O. subulatum be known once again under its very first name, Stylidium subulatum and Oreostylidium should be reduced to synonymy of Stylidium. In 2002, another study based on molecular evidence determined that in the most parsimonious cladistic tree, Stylidium graminifolium
Stylidium graminifolium
Stylidium graminifolium, the grass triggerplant, is a dicotyledonous plant that belongs to the genus Stylidium . This species used to belong to the Stylidium graminifolium complex, but the name was conserved for this single species when two others were split from the complex and introduced as new...
and O. subulatum were closely related, with O. subulatum again nested within Stylidium. Based on molecular clock
Molecular clock
The molecular clock is a technique in molecular evolution that uses fossil constraints and rates of molecular change to deduce the time in geologic history when two species or other taxa diverged. It is used to estimate the time of occurrence of events called speciation or radiation...
calculations and their data, the researchers concluded that S. graminifolium and O. subulatum shared a common ancestor about 3 million years ago. The researchers responsible for the 2002 study also concluded that Oreostylidium should be transferred to Stylidium and O. subulatum should retake its former name as Stylidium subulatum.