Dendrosenecio johnstonii

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Dendrosenecio johnstonii
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Dendrosenecio
Species:
D. johnstonii
Binomial name
Dendrosenecio johnstonii
Synonyms

See text.

Dendrosenecio johnstonii, formerly Senecio johnstonii, is a species of giant groundsel found in the middle altitudes of Mount Kilimanjaro in Africa. A recent botanical reclassification split off some species formerly in Senecio, putting the giant groundsels in the new genus Dendrosenecio. It also redefined the former species Senecio cottonii, as a subspecies of Dendrosenecio johnstonii. Both genera are in the family Asteraceae . The giant grounsels of the genus Dendrosenecio evolved, about a million years ago, from a Senecio that established itself on Mount Kilimanjaro, with those that survived adapting into Dendrosenecio kilimanjari . As it moved down the mountain, the adaptations necessary for the new environment created the new species, Dendrosenecio johnstonii. Various subspecies are found on other mountains. [2]

Contents

Description

Dendrosenecio johnstonii can be up to 10 meters tall, and grow to 40 centimeters (17 inches) or more in diameter. The centre of the stem, at full size, contains 1 to 2 centimeters of pith. It branches repeatedly, forming a dense canopy with 50 to 80 branches when mature. The leaves are hairless, heart-shaped (cordate) and large, 53 centimetres (approximately 2 feet) long by 40 centimetres (16 inches) wide.

The flower shoot is a tall, broad cone, 60 centimetres (about 2 feet) tall, and 40 centimetres (16 inches) wide, with the flower heads horizontal. Each floret is about 25 millimetres (one inch) long, and the compound flower is made up of 11 to 15 of the petal-like ray florets, with thirty to fifty "disc" florets in the centre. [3]

Distribution

D. johnstonii lives between the altitudes of 2,750 and 3,350 meters (9,000 and 11,000 feet) on Kilimanjaro. [3]

The following excerpts were presented as first hand accounts:

Kilimanjaro (1903)
"Ravines longer retain a somewhat richer vegetation. The last stunted Erica -trees disappear from them at 2,900 meters; and are replaced by a new characteristic plant of very peculiar habit, the arboreous Senecio johnstonii, with a spongy, simple or forked stem, the top of which bears a rosette of leaves as long as one's arm, and a dense inflorescence a meter in length."
"Senecio johnstonii bears the least resemblance to the alpine habit in this region. It is remarkable, however, that plants of similar habit are also found on tropical high mountains elsewhere. For the Vellozieae of Brazil are similar, and so to some extent are species of Espeletia in the Cordilleras of Venezuela.... In other respects the impress of the alpine climate is most clearly stamped on the vegetation, especially in the higher part of the region, with its dwarf plants. Protective measures against transpiration are everywhere strongly developed, in particular dense coatings of woolly hairs are frequent." [4]
Kilimanjaro (2007)
"There is no bamboo zone, nor a Hagenia - Hypericum zone. Above about 4,600 meters, very few plants are able to survive the severe conditions, although specimens of Helichrysum newii have been recorded as high as 5,760 meters (close to a fumarole), and mosses and lichens are found right up to the summit. The upland moor consists primarily of heath/scrub plants, with Erica excelsa ( Erica rossii ), Philippia trimera ( Erica trimera ), Adenocarpus mannii , Protea kilimandscharica ( Protea afra ), Stoebe kilimandscharica ( Seriphium kilimandscharicum ), Myrica meyeri-johannis ( Morella salicifolia ), and Myrsine africana . Grasses are abundant in places, and Cyperaceae form the dominant ground cover in wet hollows. On flatter areas between the upland moor and the forest edge are areas of moorland or upland grassland composed of Agrostis producta , Festuca convoluta ( Poa kilimanjarica ), Koeleria gracilis ( Koeleria capensis ), Deschampsia sp., Exotheca abyssinica and Andropogon amethystinus , with scattered bushes of Adenocarpus mannii , Kotschya recurvifolia and Myrica meyeri-johannis ( Morella salicifolia ). Various species of Helichrysum are found in the grasslands and in the upland moor. Two distinct forms of giant groundsel occur on the upper mountain: Senecio johnstonii cottonii, endemic to the mountain and only occurring above 3600 meters , and S.johnstonii johnstonii which occurs between 2,450 meters and 4,000 meters, and shows two distinct forms. At all altitudes Senecio favours the damper and more sheltered locations, and in the alpine bogs is associated with another conspicuous plant, growing up to 10m tall, the endemic giant lobelia Lobelia deckenii . Below the tree line, the park includes six corridors through the forest to the mountain foot." [5]

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<span class="mw-page-title-main">Mount Elgon National Park</span> National park in Uganda and Kenya

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<i>Dendrosenecio keniodendron</i> Species of flowering plant

Dendrosenecio keniodendron or giant groundsel is a species of the genus Dendrosenecio of the large family Asteraceae and is one of the several species of giant groundsels endemic to the high altitudes of the Afrotropics, including Dendrosenecio johnstonii (Senecio battiscombei) occurring on Mount Kilimanjaro, Mount Kenya, and the Aberdare Mountains, Dendrosenecio keniensis occurring the lower alpine zone of Mount Kenya and D. keniodendron occurring in higher and drier sites on Mount Kenya. The giant rosette plants, sometimes 6 metres (20 ft) tall, often grow in even-sized stands, with different understory communities under different-aged stands.

<i>Dendrosenecio keniensis</i> Species of plant

Dendrosenecio keniensis is one of the giant groundsels endemic the higher altitudes of Mount Kenya. It is in the family Asteraceae and the genus Dendrosenecio. Dendrosenecio keniodendron occurs the upper alpine zone of Mount Kenya and D. keniensis in the wetter areas of the lower alpine or the moorlands.

<i>Senecio keniophytum</i> Species of flowering plant

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<i>Dendrosenecio battiscombei</i> Species of flowering plant

Dendrosenecio battiscombei is one of the giant groundsels that lives on the slopes of Mount Kenya and the Aberdare Range. Like Dendrosenecio adnivalis on the Ruwenzori Mountains and the Virunga Mountains, Dendrosenecio battiscombei grows in the lower wetter areas of the Afro-Alpine zone.

<i>Dendrosenecio</i> Genus of flowering plants

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<i>Senecio angulatus</i> Species of flowering plant in the daisy family Asteraceae

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Dendrosenecio elgonensis is one of the giant groundsel of East Africa; this one is endemic to Mount Elgon. They used to be considered part of the genus Senecio but recently have been reclassified to their own genus, Dendrosenecio.

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<i>Dendrosenecio kilimanjari</i> Species of flowering plant

Dendrosenecio kilimanjari is a giant groundsel found on Mount Kilimanjaro in Africa, below 4,000 metres (13,000 ft).

<i>Dendrosenecio adnivalis</i> Species of flowering plant

Dendrosenecio adnivalis is one of the giant groundsels of the mountains of Eastern Africa. D. adnivalis grows on the Rwenzori Mountains and on the Virunga Mountains in Uganda and the Democratic Republic of Congo.

Dendrosenecio brassiciformis is a species of East African giant groundsel. It is endemic to the slopes of Aberdare Range and bearing fruit but once, and dying after. Once considered to be of the genus Senecio but since have been reclassified into their own genus Dendrosenecio.

<span class="mw-page-title-main">Natural history of Mount Kenya</span>

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<span class="mw-page-title-main">East African montane moorlands</span>

The East African montane moorlands is a montane grasslands and shrublands ecoregion which occupies several high mountain peaks in Kenya, South Sudan, Tanzania, and Uganda.

<span class="mw-page-title-main">Rwenzori–Virunga montane moorlands</span> Montane ecoregion in central Africa

The Ruwenzori-Virunga montane moorlands is a montane grasslands and shrublands ecoregion of the Rwenzori Mountains and Virunga Mountains in central Africa.

References

  1. "Index Nominum Genericorum database". International Code of Botanical Nomenclature . Smithsonian Institution. 1978. Retrieved 2008-05-04.
  2. Knox, Eric B. (2004). "Adaptive radiation of African montane plants". In Ulf Dieckmann; Michael Doebeli; Diethard Tautz; Johan A. J. Metz (eds.). Adaptive Speciation. Cambridge University Press. p. 476. ISBN   0-521-82842-2 . Retrieved 2008-03-29.
  3. 1 2 Aluka. "Entry for Dendrosenecio johnstonii (Oliv.) B.Nord". African Plants. Ithaka Harbors, Inc. Archived from the original on 2013-08-01. Retrieved 2008-05-14.
  4. Schimper, Andreas Franz Wilhelm; William Rogers Fisher; Percy Groom; Isaac Bayley Balfour (1903). "Mountain Regions in the Tropics". Plant-geography Upon a Physiological Basis. Translated by William Rogers Fisher. Clarendon Press . Retrieved 2008-05-08.
  5. World Conservation Monitoring Centre; Langdon D. Clough (2007-10-03). "Kilimanjaro National Park, Tanzania". Encyclopedia of Earth . United Nations Environment Programme . Retrieved 2008-03-27.