Oreostylidium
Oreostylidium subulatum is the only species of the monotypic genus so Oreostylidium within the Stylidiaceae. It is endemic in New Zealand.
Oreostylidium subulatum is a very small plant with rather inconspicuous and small, white flowers. Below the flower has the plant trichomes, which are constructed as well as in the closely related species of the genus Stylidium and allow them a carnivorous lifestyle. Oreostylidium subulatum is not considered carnivorous kind, but there were no relevant studies, whether it produces digestive enzymes and accordingly could be carnivorous yet.
Features
Oreostylidium subulatum is a very small plant with a height of about two to three centimeters. The sessile leaves are of linealischer to pfriemlicher form you can reach a length of 10 to 40 mm and a width of 1 to 2 mm wide and stand in a dense basal rosette of leaves. The leaves are also hairless, smooth and entire, rarely pinnate at the top. The stomata have no daughter cells ( anomocytisch ), as is the case for example with Donatia. The simple design and unbranched root has a central cylinder with four Xylempolen ( tetrarche root ). The plants form rhizomes or stolons of up to 6 cm in length, these are separated by internodes.
The very short flower stems, which does not protrude from the leaf rosette, thin and upright. It has a maximum height of two to three centimeters and is occupied by glandular trichomes that match those of the shot plants and allow for them by the digestive enzymes contained in them a carnivorous lifestyle. Bracts are sometimes present, often but not when they are very small and linear.
The inflorescence consists of a single, radial symmetry white bloom. The petals sit evenly on the flower and are in their shape and size equal to that Blütenaderung is simple and only slightly branched. The calyx is upright and compressed, besides, he is almost as wide as the ovary formed. It consists of five fused petals. The five petals are similar in construction to the flowers which is also classified into the Stylidiaceae Forstera and Phyllachne species of New Zealand.
As the plant has shot Oreostylidium a column in which the two are fused with dust the ovary consists of two carpels. The ovary is large, cylindrical and elongated. At the connection to the flower stems it is verengt.Die column is, however, unlike the shot plants immobile and unresponsive to touch.
After flowering, a 5-8 mm long forms, by measuring 4-5 mm, broadly oval to egg-shaped capsule vice versa fruit.
The set of chromosomes ( karyotype ) of Oreostylidium subulatum consists of 2n = 30 chromosomes.
Distribution and habitat
Oreostylidium subulatum is endemic to New Zealand, while maintaining the style is not as localized as the other types of Stylidiaceae, members of the genera Forstera and Phyllachne. According to a report by R. Good, 1925, the species is restricted to the South Island of New Zealand, according to previous reports, however, it was also found in the area of Ruapehu on the North Island to the South Island resources were on Swampy Hill near Dunedin and described the Grampians near Nelson.
In their habitat Oreostylidium is subulatum as the types of Forstera and Phyllachne to the montane and subalpine altitudinal limits. The species is classified as not at risk in New Zealand.
About the settlement of New Zealand by Oreostylidium subulatum and the other types of Stylidiaceae there were a few years ago very different opinions. So Wardle went in 1968 from the fact that the ancestors of these species have already lived as evolutionarily very old genres to Antarctica and New Zealand are said to have reached over Tasmania. The ancestors are said to have survived on depleted soils of high altitudes, before they trained in the Pliocene to montane species. Raven 1973 deems it likely that montane species have drifted only during the outbound through the collision of the Australian plate with the Eurasian plate orogeny in the Pleistocene or late Pliocene through Australia to New Zealand and were able to establish in habitats newly created. Because of molecular biological results on the relationship analysis of Oreostylidium subulatum and those based in Australia shot plants ( Stylidium ) today adopted a development style from about three million years ago, and a drifting of the ancestral species from the Australian mainland.
History of Science and systematics
Discovery and classification
The first description of Oreostylidium subulatum was made in 1864 by William Jackson Hooker as Stylidium subulatum in the genus Stylidium. The classification was made on the basis of individuals without flowers and he was referring to in the classification on the morphology of the fruit as well as similarities between the environmental demands on the habitat. Within the genus he placed the type due to the fruit morphology in the subgenus Tolypangium. In 1878, Ferdinand von Mueller Stylidium subulatum presented due to the floral morphology in the related genus Phyllachne and in the same year Sven Berggren placed it as the only way in which he described new monotypic genus Oreostylidium.
In 1887 William Colenso described a second species of the genus and named it Oreostylidium affinity, based on morphological differences with the previous descriptions of Oreostylidium subulatum. He already figured in the description that he was not quite sure about the new type, but differed the present him copies of the descriptions by Berggren and Hooker. O. affine was taken subulatum later as a synonym for Oreostylidium.
The current debate about the flower morphology and molecular biological findings suggest a new classification close to the genus Stylidium, where the species should be included as sister species of Stylidium graminifolium. Accordingly, it is likely that Oreostylidium will be subulatum out with the next revision of Stylidiaceae again under their first name Stylidium subulatum of 1864.
Oreostylidium and Stylidium
Because of the similarities in flower structure was proposed subulatum take Oreostylidium in the genus Stylidium, but this was rejected due to the significant differences. According to some researchers Oreostylidium to subulatum represent an extreme form of the so-called Pädomorphose, the flower structure should therefore be derived from a very early stage of flower development to full Stylidium flower. Alternatively, it is contemplated that the flower could be a reduction result. This process should have taken place by the isolation of the species in New Zealand. The entire population of Oreostylidium subulatum is therefore a very small founder population, in extreme cases, due to a single seed, which was drifted from Australia to New Zealand. The new habitat and especially the absence of the typical in Australia pollinator species to which the highly specialized flowers of Stylidium species are adapted to a complete change in floral morphology occurred in the founder population towards unspecific bestäubbaren flowers. These flowers allow different from the flowers of Stylidium species an obligate self-fertilization.
These considerations are supported by molecular studies, graminifolium identify the Oreostylidium subulatum as sister species of Stylidium. On the basis of various genes of the chloroplast DNA rbcL and ndhF, could 1998 be noted that Oreostylidium subulatum was filed within the Stylidium species resulting in all pedigrees. In 2002 also a close relationship between Stylidium graminifolium and Oreostylidium was found subulatum that could be identified as sister species within the genus Stylidium. About the genetic difference between the two species was calculated that the Artspaltung supposed to have taken place from a common ancestral species that will have anatomically suited Stylidium graminifolium in two ways about three million years ago. Based on these results, a return of Oreostylidium was subulatum required in the genus Stylidium.