Thomandersia
| Thomandersia | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Thomandersiaceae | ||||||||||||
| Sreem. | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Thomandersia | ||||||||||||
| Baill. |
Thomandersia is a genus of the order of Lippenblütlerartigen (Laminales). The genus was named in honor of the Scottish doctor and botanist Thomas Anderson (1832-1870). The six species differentiated within the genus occur only in parts of central and west Africa .
The position of the genus within the order was disputed for a long time, mostly they were assigned to the acanthus family . Molecular biological methods, however, support a classification into a monotypical family Thomandersiaceae .
description
Vegetative characteristics
Thomandersia species are slender shrubs , small trees or occasionally lianas that reach a height of 0.5 to 15 m. The trunk is round and can be hairy on young plants. The nodes are flattened and have no stipules or articulated connections. The plants do not contain any milky sap .
The simple leaves are opposite or cross-opposite, the opposite leaves come in more or less different shapes. Usually they are clearly stalked, only occasionally they are almost sessile. The leaf blades are elongated, elliptical, inverted ovoid or occasionally circular or lanceolate. The tip is pointed or bulged. The base is wedge-shaped to rounded. The smaller leaves of a pair of leaves are sometimes heart-shaped, more or less leathery and irregularly provided with non-translucent glands. Both surfaces are colored differently, on the upper side there may be a few isolated trichomes , the underside can be finely hairy, especially on the leaf veins. The leaf margin has entire margins or has a few blunt teeth, which are then usually near the tip. The midrib is protruding on the underside and sunk on the top, the primary side veins are pinnate, in between the secondary side veins are network-like. Tufted domatia can often be found on the armpits between the midrib and the side veins .
Inflorescences and flowers
The inflorescences are upright, terminal or axillary grapes , which are dense and pyramidal or more or less loosely built. The flowers are almost sessile to stalked, irregularly arranged either opposite or in whorls of three flowers. The bracts are about 1 mm long, triangular-awl-shaped and hairy. The bracts are shorter than 1 mm, awl-shaped, ciliate and stand on the sides of the calyx .
The chalice is bell-shaped and decorated with five short, triangular lobes. It is green, purple or brown in color and fleshy. The surface can be hairy, the edge is ciliated. It persists on the fruit, enlarges and forms one or two swollen hills on the side facing away from the axis, each with one or two more or less noticeable openings. The zygomorphic , two-lobed, slightly leathery crown is 10 to 20 mm long and colored green, white, yellow, orange, red, pink or purple, often with darker stripes. The corolla tube can be hairy and is slightly bumpy on the axially facing side near the base. The upper lip is two-lobed, the lower lip is three-lobed and more or less concave or provided with protruding lateral lobes. The lobes themselves have entire margins or sometimes have wavy edges and glandular hairs.
The four stamens occur in two lengths and are between the corolla lobes. They do not or only slightly protrude from the crown. The stamens are fused with the corolla tube. They can be hairless, glandular or finely haired. The anthers consist of two counters, the stamens start dorsally (on the back). The dust bags open through outwardly facing longitudinal slits. The pollen grains are elliptical-spherical, flattened at the poles and dotted on the surface or five- or six-colp. In addition to the stamens, a single, awl-shaped staminodium is formed, which is shorter than 1 mm.
The ovary is perennial, superordinate and two-fold, the placentation is axial. Each ovary compartment contains two or three ovules surrounded by the placenta . The ovary is swollen at the base, the tissue carries nectar, but there is no flower base. The ovary is hairless, hairy glandular or provided with attached hair, it has a single stylus that ends in a cylindrical or bilobed stigma .
Fruits and seeds
The fruits are almost spherical to elliptical, conical or egg-shaped capsules that are dry, woody and brown-black when ripe. The walls are up to 1.5 mm thick, they spring open lengthways in two flaps.
The seeds are black, brown, orange, yellow or cream colored. Their shape is spherical or ovoid to elliptical, their diameter is 2 to 5 mm. The surface of the seeds is provided with triangular scales or spirally arranged, rounded warts. The seeds have a flattened and elongated extension of the seed stalk (funicle) with a width of up to 2 mm and a length of up to 5 mm.
Distribution and locations
The species of the genus are distributed in western and central Africa, they occur in southeastern Nigeria , southern Cameroon , Gabon , Equatorial Guinea , the Democratic Republic of the Congo , the Republic of the Congo and the Central African Republic . Thomandersia anachoreta occurs disjoint from the rest of the species of the genus in Liberia and Ivory Coast .
These distribution areas support the hypothesis of a Guineo-Congolian phytogeographic region. Various disjunctions and centers of endemism can be identified both between individual species and within species . The Dahomey Gap is also clearly pronounced within the entire genus .
The locations of the species are in the shrub layer of evergreen, partly deciduous, mixed, wet or dry forests, gallery forests , along rivers, coasts, floodplains, plains and highland forests and forest remnants. They are mainly to be found there at the edges of the forest, in clearings, disturbed areas and along roads. They grow on loamy, rocky, laterite , clays , sandy, calcareous, granite or iron-rich soils.
ecology
The plants are usually found in abundance at the locations, occasionally they form dense clusters or thickets by forming adventitious roots at the nodes and sprouting again from severed stumps.
The plants are eaten by various types of mammals, such as bongos ( Tragelaphus eurycerus ) and forest elephants ( Loxodonta cyclotis ). Chimpanzees ( Pan troglodytes ) use twigs or young sprouts of Thomandersia hensii to poke into termite mounds before looking for termites themselves.
Ants have been observed on the nectaries of the chalice. On the crowns of Thomandersia hensii there are often punctures that indicate nectar theft.
Systematics
External system
Molecular biological investigations confirm the classification of Thomandersia in the order of the mint-like family (Lamiales), but the genus could not be classified in one of the recognized families of the order. The studies suggest that there is a connection between the genus and the Schlegeliaceae , but so far only weak indications have been found for this classification.
Internal system
Six types are distinguished within the genus:
- Thomandersia anachoreta Heine : It was first described by the Ivory Coast and Liberia.
- Thomandersia butayei De Wild.
- Thomandersia congolana De Wild. & T.Durand
- Thomandersia hensii De Wild. & T.Durand
- Thomandersia laurentii De Wild.
- Thomandersia laurifolia T. Anderson ex Benth.
The type species of the genus is Thomandersia laurifolia .
Botanical history
The genus Thomandersia was first described in 1876 by George Bentham under the name Scytanthus . However, since this name had already been assigned by William Jackson Hooker in 1844 for a genus from the silk plant family (Asclepiadaceae), the genus was renamed by Henri Ernest Baillon in 1891 and was given the name Thomandersia , which is valid today .
The first description of the genus described only a single species Scytanthus laurifolius (= Thomandersia laurifolia ), around the turn of the 20th century, four more species were described by Émile Auguste Joseph De Wildeman and Théophile Alexis Durand . A sixth species was described in 1966 by Hermann Heino Heine in his revision of the genus.
The taxonomic position of the genus has long been controversial, most authors assigned the genus to the Acanthus family (Acanthaceae), since the seeds of Thomandersia have the enlarged seed stalks that actually only occur within this family. Due to the similar pollen morphology, the genus was also assigned to the sesame family (Pedaliaceae) by some authors .
Due to the independence of the genus, mainly in the morphology of the leaves and the anthers, the genus was described in 1977 by CP Sreemadhaven as the only genus of the monotypical family Thomandersiaceae. The independence within the order of the mint-like family (Lamiales), confirmed by molecular biological investigations, led to Alexandra H. Wortley et al. affirmed the status of a monogeneric family in their revision published in 2007.
literature
- Alexandra H. Wortley, David J. Harris, and Robert W. Scotland: On the Taxonomy and Phylogenetic Position of Thomandersia . In: Systematic Botany , Vol. 32 (2008), Number 2, pp. 415-444, ISSN 0363-6445 , doi : 10.1600 / 036364407781179716
Individual evidence
- ↑ Lotte Burkhardt: Directory of eponymous plant names . Extended Edition. Botanic Garden and Botanical Museum Berlin, Free University Berlin Berlin 2018. [1]