Dahlgrenodendron
Encyclopedia
Dahlgrenodendron is an endangered genus of plant
in family Lauraceae
. They are evergreen
"lauroide" trees belonging to the tropical or templated Laurel forest
habitat, a type of Cloud forest
in Africa and South Africa.
. professor
at the University of Copenhagen
, that found the first species of genus in Luarel forest habitat in Eastern Cape Province, KwaZulu-Natal, South Africa.
The genus is characterized by an extremely rare combination of characters that have occurred in the species in its own distinct genus. There is little information regarding the species due to its scarcity, 200 individuals.
The species Dahlgrenodendron natalense is endangered and is known from a scarce number of localities; it has not been found again at Ngoye forest, despite several searches and it is probably extinct at this locality; there are at least two plants in the Nqutu area; a single large tree, which is dying of old age, is in Umdoni Park; the largest number of trees are found in the remnant forest patches between the Msikaba and Umtamvuna Rivers. Dahlgrenodendron is adapted to extreme conditions in semi-arid climate but mostly depending on favorable soil edaphic conditions, as presence of aquifers, groundwater periodic flows, periodically flooded forests in sand almost without nutrients.
Dahlgrenodendron trees are laurel forest evergreen hermaphodyte tall trees with leaves opposite, penninerved, net-veining conspicuous on both surfaces. Inflorescences 3-flowered cymules, arranged on young growth or on short-shoots, with small, caducous bracts. The flowers are bisexual, 3-merous, greenish white. Perianth: tube deeply urceolate. Tepals subequal. Male flowers with 9 fertile stamens, the third whorl with glands; filaments much shorter than anthers; anthers 2-thecous, the first and second whorl introrse, the third whorl extrorse; pollen with a well developed, striate exine, apparently unique for the family Lauraceae; staminodes of whorl four conspicuous, ovate-triangular. Ovary sessile, more or less immersed in a receptacle, narrowed into slender style and small stigma. the fruit completely enclosed in accrescent perianth tube; tepals persistent. The fruit, a berry, is dispersed by birds. Seed with a delicate testa.
n monotypic Dahlgrenodendron plant genus come from a relict species living in the Tertiary in a more warmer and humid climate conditions in the continent, in the Cape province area of laurel forest, and therefore, more distributed in the Tertiary.
It is a palaeo endemic botanical genus, usually found on forest margins, both next to and away from stream banks. A few individuals have been recorded from within climax forest, but these were invariably very old and senescent.
The ecological requirements of the genus are those of the laurel forest
and like most of their counterparts laurifolia in the world, it is vigorous species with a great ability to populate the habitat that is conducive. The natural habitat is rainforest which is cloud-covered for much of the year. The species is found in forests that face threats of destruction by human deforestation
.
Because of the special lack of worldwide knowledge about the family lauraceae
in general, very little is known about their diversity. Recent monographs of the small and medium genera of lauraceae with up to 100 species per genus have produced a high increase in the number of known species. This high increase is expected for other genera as well, particularly for those with more than 150 species recorded, bringing an expected considerable increase in the total number of species of the family.
A related vegetal community evolved millions of years ago on the supercontinent of Gondwana
, and species of this community are now found on several separate areas of the Southern Hemisphere
, including South America
, Africa
, New Zealand
, Australia
and New Caledonia
.
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
in family Lauraceae
Lauraceae
The Lauraceae or Laurel family comprises a group of flowering plants included in the order Laurales. The family contains about 55 genera and over 3500, perhaps as many as 4000, species world-wide, mostly from warm or tropical regions, especially Southeast Asia and South America...
. They are evergreen
Evergreen
In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.There are many different kinds of evergreen plants, both trees and shrubs...
"lauroide" trees belonging to the tropical or templated Laurel forest
Laurel forest
Laurel forest is a subtropical or mild temperate forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterized by tree species with evergreen, glossy, enlongated leaves, known as laurophyll or lauroide...
habitat, a type of Cloud forest
Cloud forest
A cloud forest, also called a fog forest, is a generally tropical or subtropical evergreen montane moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level. Cloud forests often exhibit an abundance of mosses covering the ground and...
in Africa and South Africa.
Overview
The genus name, is dedicated to Rolf DahlgrenRolf Dahlgren
Rolf Martin Theodor Dahlgren was a Swedish-Danish botanist, professor at the University of Copenhagen from 1973 to his death....
. professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...
at the University of Copenhagen
University of Copenhagen
The University of Copenhagen is the oldest and largest university and research institution in Denmark. Founded in 1479, it has more than 37,000 students, the majority of whom are female , and more than 7,000 employees. The university has several campuses located in and around Copenhagen, with the...
, that found the first species of genus in Luarel forest habitat in Eastern Cape Province, KwaZulu-Natal, South Africa.
The genus is characterized by an extremely rare combination of characters that have occurred in the species in its own distinct genus. There is little information regarding the species due to its scarcity, 200 individuals.
The species Dahlgrenodendron natalense is endangered and is known from a scarce number of localities; it has not been found again at Ngoye forest, despite several searches and it is probably extinct at this locality; there are at least two plants in the Nqutu area; a single large tree, which is dying of old age, is in Umdoni Park; the largest number of trees are found in the remnant forest patches between the Msikaba and Umtamvuna Rivers. Dahlgrenodendron is adapted to extreme conditions in semi-arid climate but mostly depending on favorable soil edaphic conditions, as presence of aquifers, groundwater periodic flows, periodically flooded forests in sand almost without nutrients.
Dahlgrenodendron trees are laurel forest evergreen hermaphodyte tall trees with leaves opposite, penninerved, net-veining conspicuous on both surfaces. Inflorescences 3-flowered cymules, arranged on young growth or on short-shoots, with small, caducous bracts. The flowers are bisexual, 3-merous, greenish white. Perianth: tube deeply urceolate. Tepals subequal. Male flowers with 9 fertile stamens, the third whorl with glands; filaments much shorter than anthers; anthers 2-thecous, the first and second whorl introrse, the third whorl extrorse; pollen with a well developed, striate exine, apparently unique for the family Lauraceae; staminodes of whorl four conspicuous, ovate-triangular. Ovary sessile, more or less immersed in a receptacle, narrowed into slender style and small stigma. the fruit completely enclosed in accrescent perianth tube; tepals persistent. The fruit, a berry, is dispersed by birds. Seed with a delicate testa.
Ecology
The South AfricaSouth Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
n monotypic Dahlgrenodendron plant genus come from a relict species living in the Tertiary in a more warmer and humid climate conditions in the continent, in the Cape province area of laurel forest, and therefore, more distributed in the Tertiary.
It is a palaeo endemic botanical genus, usually found on forest margins, both next to and away from stream banks. A few individuals have been recorded from within climax forest, but these were invariably very old and senescent.
The ecological requirements of the genus are those of the laurel forest
Laurel forest
Laurel forest is a subtropical or mild temperate forest, found in areas with high humidity and relatively stable and mild temperatures. They are characterized by tree species with evergreen, glossy, enlongated leaves, known as laurophyll or lauroide...
and like most of their counterparts laurifolia in the world, it is vigorous species with a great ability to populate the habitat that is conducive. The natural habitat is rainforest which is cloud-covered for much of the year. The species is found in forests that face threats of destruction by human deforestation
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
.
Because of the special lack of worldwide knowledge about the family lauraceae
Lauraceae
The Lauraceae or Laurel family comprises a group of flowering plants included in the order Laurales. The family contains about 55 genera and over 3500, perhaps as many as 4000, species world-wide, mostly from warm or tropical regions, especially Southeast Asia and South America...
in general, very little is known about their diversity. Recent monographs of the small and medium genera of lauraceae with up to 100 species per genus have produced a high increase in the number of known species. This high increase is expected for other genera as well, particularly for those with more than 150 species recorded, bringing an expected considerable increase in the total number of species of the family.
A related vegetal community evolved millions of years ago on the supercontinent of Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
, and species of this community are now found on several separate areas of the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
, including South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, 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...
, 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 Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
.
Species
It contains the following species (but this list may be incomplete):- Dahlgrenodendron natalense, W. Burger