Tetroncium magellanicum
| Tetroncium magellanicum | ||||||||||||
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Tetroncium magellanicum , illustration by Walter Hood Fitch |
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| Scientific name of the genus | ||||||||||||
| Tetroncium | ||||||||||||
| Willd. | ||||||||||||
| Scientific name of the species | ||||||||||||
| Tetroncium magellanicum | ||||||||||||
| Willd. |
Tetroncium magellanicum is arepresentative of the monocot plants fromthe trident family (Juncaginaceae) that occursonly in South America . Of the other members of the family, it differs in the dioecious and the flowers twofold whorl .
features
Vegetative characteristics
Tetroncium magellanicum is a perennial , bare plant with a rhizome . It becomes 5 to 25 (rarely up to 35) cm high. The rhizome is ascending, up to 20 cm long and has a diameter of 2 to 4 (rarely up to 6) mm. At the top, the rhizome forms above-ground shoots. The rungs are ascending or upright and branch out near the base. They are densely covered with brown remnants of leaves, the leaves are close to the tip.
The leaves stand in two lines (distich) and are riding (sword leaf ). They are simple and linear-sword-shaped with a pointed end. They are 20 to 100 (rarely 15 to 120) mm long and 1.5 to 3 mm thick. They are stiff and leathery, with no ligules or auricles at the base .
Inflorescences and flowers
The plants are dioecious, separate sexes ( diocesan ), the inflorescence is on a shaft. The shaft is erect, 25 to 200 (rarely up to 250) mm long. The inflorescences are terminal, are dense and around 10 to 50 mm long. The ears are without bracts and consist of up to 30 flowers . A flower stalk is missing or is a maximum of 0.5 mm long.
The male flower has four yellowish tepals with reddish brown points. They are concave or shell-shaped, broadly ovate, pointed or subobtus. They are 1.2 to 2 × 0.5 to 1.5 mm in size. The four stamens sit opposite the tepals and at their base. You are (almost) sitting. The anthers are yellowish and extrors. The pollen consists of monads, is approximately spherical, inaperturate and has a reticulate exine.
The female flower also has four tepals, which are similar to those of the male flower, but are narrower, ovate to ovate-lanceolate. There are four carpels , about half of which are connected at the base. Each carpel has a basal, anatropic ovule . The stylus point away from each other.
fruit
The fruit is fourfold, dry, a closing fruit. The color is a reddish brown. It is narrowly conical with long, beak-shaped styluses. It is 4 to 8 (rarely 10) mm long and around 1 mm wide. It is smooth and mostly lonely. The seeds are anatropic, brown, narrow ovate and have an endosperm.
distribution
Tetroncium magellanicum is restricted to the southern hemisphere. The main area is in southern South America ( Patagonia and Tierra del Fuego ). To the north, the area extends to around 40 ° south latitude in western Argentina and around 37 ° in Chile . The northernmost known occurrences are in the national parks Nahuel Huapi in the Andes, Nahuelbuta and Chiloé in Chile. There are other occurrences on the Falkland Islands (West and East Falkland), but the species is missing in the Lafonia region on East Falkland, probably due to the dry summer there. There are also occurrences on Gough Island in the South Atlantic Ocean, but the species is absent on the other islands of the Tristan da Cunha group.
Locations and ecology
Tetroncium magellanicum grows in different types of bog , preferably in Sphagnum bogs and raised bogs. These moors are part of the characteristic vegetation of Tierra del Fuego known as "Magellanic Moorland". Tetroncium magellanicum often grows in the raised bogs dominated by Sphagnum magellanicum . T. magellanicum is found mainly in the wetter areas, where it often occurs together with Carex magellanica . In the Pacific moors, which are dominated by cushion-forming vascular plants, Tetroncium is associated with Astelia pumila , Donatia fascicularis or Drosera uniflora .
These types of bog are widespread from the southern tip of the continent to about 43 ° south latitude, and from sea level to the tree line. It also occurs further north in moors. In southern Chile, where the moors alternate with sub-Antarctic evergreen forest with Nothofagus betuloides , and further east, where the moors alternate with deciduous forest ( Nothofagus pumilio and Nothofagus antarctica ), Tetroncium is also found in clearings and open parts of these forests.
In the Falkland Islands, tetroncium grows in bogs, dwarf shrub heaths and acidic meadows. On Gough Island, it is one of the few common flowering plants found in high bogs.
Usually the species grows below 500 m above sea level. Higher locations up to 1300 m above sea level are only known from the northernmost distribution area.
Tetroncium tolerates frequent and prolonged flooding. Sometimes only the upper leaves and the inflorescences protrude from the water. The locations are also extremely poor in nutrients.
Systematics and botanical history
The genus Tetroncium is part of the Juncaginaceae family . Within the family, it is the sister group of the other two genera, Triglochin and Cycnogeton .
The only representative of the genus is Tetroncium magellanicum .
Species and genus were first described in 1808 by Carl Ludwig Willdenow on the basis of material that Philibert Commerson had collected in the Strait of Magellan . Commerson had accompanied Louis Antoine de Bougainville on his circumnavigation of the world from 1766 to 1769. Willdenow had received the material for the first description from Martin Vahl in Copenhagen.
The species was mentioned in several reports on research trips to southern South America. Buchenau has contributed a lot to the knowledge of the species. Nevertheless, the statement by P. Barry Tomlinson from 1982 was still valid in 2013 that little is actually known about the species. Embryological and karyological data, for example, are completely absent, and the development of flowers and fruits is unknown. Little is known about the mechanisms of spread.
Individual evidence
- ↑ a b c d e f g h i j k l m n Sabine von Mering: Tetroncium and its only species, T. magellanicum (Juncaginaceae): distribution, ecology and lectotypification . Willdenowia 2013, Volume 43, pp. 13-24.
- ↑ a b c Donald H. Les, Nicholas P. Tippery: In time and with water ... the systematics of alismatid monocotyledons . In: P. Wilkin, SJ Mayo: Early Events in Monocot Evolution . Cambridge University Press 2013, pp. 118-164.
- ^ A b c Sabine von Mering, Joachim W. Kadereit: Phylogeny, systematics and recircumscription of Juncaginaceae - a cosmopolitan wetland family . In: Seberg, Petersen, Barfod and Davis (eds.): Diversity, Phylogeny, and Evolution in the Monocotyledons . Aarhus University Press, Aarhus, Denmark, pp. 55-79. (PDF)
- ^ Anna Trias-Blasi, William J. Baker, Anna L. Haigh, David A. Simpson, Odile Weber, Paul Wilkin: A genus-level phylogenetic linear sequence of monocots . Taxon, 2015, Volume 64, pp. 552-581. doi : 10.12705 / 643.9
