Dendrosenecio
Encyclopedia
Dendrosenecio is a genus
of flowering plants belonging to the family
Asteraceae
. It is a segregate
of Senecio
, in which it formed the subgenus
Dendrosenecio. Its members, the giant groundsels, are endemic to the higher altitude zones of ten mountain groups in equatorial East Africa, where they form a conspicuous element of the flora.
They have a giant rosette habit, with a terminal leaf rosette at the apex of a stout woody stem. When they bloom, the flowers form a large terminal inflorescence. Concomitantly, two to four lateral branches are normally initiated. As a result, old plants have the appearance of candelabras the size of telephone poles, each branch with a terminal rosette.
and Mount Meru
in Tanzania
, Mount Kenya
, the Aberdare Range
, and Cherangani Hills
in Kenya
, Mount Elgon
on the Uganda
/Kenya border, the Ruwenzori Mountains on the Uganda/Democratic Republic of Congo (DRC) border, the Virunga Mountains
on the borders of Rwanda
, Uganda and the DRC, and Mitumba Mountains
(Mount Kahuzi
and Mount Muhi) in the east of the DRC.
With the exception of D. eric-rosenii, which occurs on several of the mountains of the Albertine Rift (Rumenzori, Virunga and Mitumba Mountains), and D. battiscombei and D. keniodendron, which are shared by Mount Kenya and the Aberdare Range, the species are individually confined to a single range. In several of the ranges different species, or subspecies, are found at different heights.
and eastern Africa
are an almost ideal model system for studying speciation
and adaptation
in plants. The mountains rise far above the surrounding plains and plateaus,
tall enough to reach above the tree line
forming "islands in the sky" or isolated habitats.
These predominantly volcanic peaks further simplify the model by their age and arrangement around the Lake Victoria
basin and proximity to the equator
.
The species found on Mount Kenya
are by far the best model for altitudinal variation. Dendrosenecio keniodendron is the species which grows at the highest of altitudes, Dendrosenecio keniensis is found at the lower altitudes of the range where the species grows and Dendrosenecio battiscombei grows at the same altitudes as D. keniensis but in the wetter environments. The other mountains which are not tall enough to have a "big one at the top" have the two, one species for the drier land and one for the damper environments or just one because the environment is not so extreme. This simplification works extremely well as an introduction to the giant groundsel of East Africa with one exception, Kilimanjaro who has the one species that lives at the top and only one species that lives below; subspecies and varieties living in the moister environments.
Gridded Adaptive Speciation Studies: Each mountain has a vertical gradient of precipitation and temperature fluctuations.Mount Kilimanjaro
at 5,985 metres (19,640 ft), Mount Kenya
at 5,198 metres (17,050 ft) and Ruwenzori at 5,109 metres (16,760 ft)) are the three tallest mountains in Africa; each tall enough to support altitude based layers of vegetative zones. Each mountain providing its own vertically placed array of isolated habitats.
Dispersal and establishment:
or convergent evolution
and repeated convergent evolution between these two groups; providing evidence that the unusual features of these plants are an evolutionary response to a challenging habitat
and an environment
which can be easily described for biogeographic
analysis.
among the 40 recorded giant senecio collections (40 accessions), yet as a group they differ significantly from Cineraria deltoidea
, the closest known relative.
The gametophytic
chromosome number (is the number of chromosomes in each cell) for the giant Dendrosenecio is n = 50, and for the giant lobelias (specifically Lobeliaceae
, Lobelia
subgenus Tupa
section Rhynchopetalum it is n = 14. Only five of the 11 species of giant senecio and three of the 21 species of giant lobelia from eastern Africa remain uncounted. Although both groups are polyploid
, Dendrosenecio is presumed to be decaploid (ten sets; 10x) and the Lobelia more certainly tetraploid (four sets; 4x), their adaptive radiation
s involved no further change in chromosome number. The cytological
uniformity within each group, while providing circumstantial evidence that they descended from a single ancestor and simplifying interpretations of cladistic analyses, provides neither positive nor negative support for a possible role of polyploidy in evolving the giant-rosette growth-form.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of flowering plants belonging to the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Asteraceae
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
. It is a segregate
Segregate (taxonomy)
In taxonomy, a segregate, or a segregate taxon is created when a taxon is split off, from another taxon. This other taxon will be better known, usually bigger, and will continue to exist, even after the segregate taxon has been split off...
of Senecio
Senecio
Senecio is a genus of the daisy family that includes ragworts and groundsels. The flower heads are normally rayed, completely yellow, and the heads are borne in branched clusters...
, in which it formed the subgenus
Subgenus
In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...
Dendrosenecio. Its members, the giant groundsels, are endemic to the higher altitude zones of ten mountain groups in equatorial East Africa, where they form a conspicuous element of the flora.
They have a giant rosette habit, with a terminal leaf rosette at the apex of a stout woody stem. When they bloom, the flowers form a large terminal inflorescence. Concomitantly, two to four lateral branches are normally initiated. As a result, old plants have the appearance of candelabras the size of telephone poles, each branch with a terminal rosette.
Species
Dendrosenecio varies geographically between mountain ranges, and altitudinally on a single mountain. There has been disagreement among botanists as to which populations of Dendrosenecio warrant recognition as species, and which should be relegated to the status of subspecies or variety. The following list, taken from Knox & Palmer will be used for articles about this genus.- Dendrosenecio adnivalisDendrosenecio adnivalisDendrosenecio adnivalis is one of the giant groundsels of the mountains of Eastern Africa. D. adnivalis grows on the Ruwenzori Mountainsand on the Virunga Mountainsin Uganda and the Democratic Republic of Congo....
(Stapf) E.B.Knox (1993) - Dendrosenecio battiscombeiDendrosenecio battiscombeiDendrosenecio battiscombei is one of the giant groundsels that lives on the slopes of Mount Kenya and the Aberdare Range...
(R.E.Fr. & T.C.E.Fr.) E.B.Knox (1993) - Dendrosenecio brassiciformisDendrosenecio brassiciformisDendrosenecio brassiciformis is one of the East African giant groundsel, this one is endemic to the slopes of Aberdare Range and bearing fruit but once, and dying after...
(R.E.Fr. & T.C.E.Fr.) Mabb. (1986) - Dendrosenecio cheranganiensisDendrosenecio cheranganiensisDendrosenecio cheranganiensis is one of the East African giant groundsel, this one endemic to the Cherangani Hills. Once it was a genus of Senecio but has recently been reclassified as a Dendrosenecio.-Description:...
(Cotton & Blakelock) E.B.Knox (1993) - Dendrosenecio elgonensisDendrosenecio elgonensisDendrosenecio 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 Senecio genus but recently have been reclassified to their own genus Dendrosenecio.-Description:...
(T.C.E.Fr.) E.B.Knox (1993) - Dendrosenecio erici-roseniiDendrosenecio erici-roseniiDendrosenecio erici-rosenii one of the East African giant groundsel and this one can be found on the Ruwenzori Mountains, Virunga Mountains and the Mitumba Mountains. A species of the genus Dendrosenecio and is also a collection of reclassified Senecio species.-Description:Dendrosenecio...
(R.E.Fr. & T.C.E.Fr.) E.B.Knox (1993) - Dendrosenecio johnstoniiDendrosenecio johnstoniiDendrosenecio johnstonii, formerly Senecio johnstonii, is a 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...
(Oliv.) B.Nord. (1978) - Dendrosenecio keniensisDendrosenecio keniensisDendrosenecio keniensis Dendrosenecio keniensis Dendrosenecio keniensis (syn. Senecio keniensis and S. brassica is one of the giant groundsels endemic the higher altitudes of Mount Kenya. It is in the family Asteraceae and the genus Dendrosenecio (previously a Senecio). Dendrosenecio keniodendron...
(Baker f.) Mabb. (1986) - Dendrosenecio keniodendronDendrosenecio keniodendronDendrosenecio 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 Afrotropic, including Dendrosenecio johnstoniioccurring on Mount Kilimanjaro, Mount Kenya,...
(R.E.Fr. & T.C.E.Fr.) B.Nord. (1978) - Dendrosenecio kilimanjariDendrosenecio kilimanjariDendrosenecio kilimanjari is a giant groundsel found atop Mount Kilimanjaro in Africa. It was originally known as Senecio kilimanjari, but a recent botanical reclassification split off some species formerly in Senecio, putting it and various other species in the new genus Dendrosenecio. Both genera...
(Mildbr.) E.B.Knox (1993) - Dendrosenecio meruensisDendrosenecio meruensisDendrosenecio meruensis is one of the East African giant groundsel, this one is endemic to the slopes of Mount Meru. Once they were considered to be of the genus Senecio but since then have been reclassified into their own genus Dendrosenecio....
(Cotton & Blakelock) E.B.Knox (1993)
Distribution
The giant groundsels are found in the alpine zone of the mountains of equatorial East Africa - Mount KilimanjaroMount Kilimanjaro
Kilimanjaro, with its three volcanic cones, Kibo, Mawenzi, and Shira, is a dormant volcano in Kilimanjaro National Park, Tanzania and the highest mountain in Africa at above sea level .-Geology:...
and Mount Meru
Mount Meru (Tanzania)
Mount Meru is an active stratovolcano located west of Mount Kilimanjaro in the nation of Tanzania. At a height of , it is visible from Mt Kilimanjaro on a clear day, and is the tenth highest mountain in Africa. Much of its bulk was lost about 8,000 years ago due to an eastward volcanic blast,...
in Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
, Mount Kenya
Mount Kenya
Mount Kenya is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian , Nelion and Point Lenana . Mount Kenya is located in central Kenya, just south of the equator, around north-northeast of the capital Nairobi...
, the Aberdare Range
Aberdare Range
The Aberdare Range is a 160 km long mountain range of upland, north of Kenya's capital Nairobi with an average elevation of . It is located in west central Kenya, northeast of Naivasha and Gilgil and just south of the Equator...
, and Cherangani Hills
Cherangani Hills
Cherangani Hills, gently rolling slopes in the western highlands of Kenya, are one of Kenya's five main forests. The highlands, the large central plateau, is divided by the Mau Escarpment rising from the border with Tanzania up to the Cherangani Hills, fencing the plateau that rises to the slopes...
in Kenya
Kenya
Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...
, Mount Elgon
Mount Elgon
Mount Elgon is an extinct shield volcano on the border of Uganda and Kenya, north of Kisumu and west of Kitale.- Physical features :It is the oldest and largest solitary volcano in East Africa, covering an area of around 3500 km²....
on the Uganda
Uganda
Uganda , officially the Republic of Uganda, is a landlocked country in East Africa. Uganda is also known as the "Pearl of Africa". It is bordered on the east by Kenya, on the north by South Sudan, on the west by the Democratic Republic of the Congo, on the southwest by Rwanda, and on the south by...
/Kenya border, the Ruwenzori Mountains on the Uganda/Democratic Republic of Congo (DRC) border, the Virunga Mountains
Virunga Mountains
The Virunga Mountains are a chain of volcanoes in East Africa, along the northern border of Rwanda, the Democratic Republic of the Congo and Uganda. The mountain range is a branch of the Albertine Rift, a part of the Great Rift Valley. They are located between Lake Edward and Lake Kivu...
on the borders of Rwanda
Rwanda
Rwanda or , officially the Republic of Rwanda , is a country in central and eastern Africa with a population of approximately 11.4 million . Rwanda is located a few degrees south of the Equator, and is bordered by Uganda, Tanzania, Burundi and the Democratic Republic of the Congo...
, Uganda and the DRC, and Mitumba Mountains
Mitumba Mountains
The Mitumba Mountain range stretches along the Western Rift Valley in Burundi and Eastern Congo , west of lake Tanganyika. The two main peaks, Mount Kahuzi and Mount Biéga are extinct volcanoes.-References:...
(Mount Kahuzi
Mount Kahuzi
Mount Kahuzi is an extinct volcano in the Democratic Republic of the Congo.It is within the Biega - Kahuzi National Park, a World Heritage Site.-Location:Mount Kahuzi was last active at the end of the Pleistocene....
and Mount Muhi) in the east of the DRC.
With the exception of D. eric-rosenii, which occurs on several of the mountains of the Albertine Rift (Rumenzori, Virunga and Mitumba Mountains), and D. battiscombei and D. keniodendron, which are shared by Mount Kenya and the Aberdare Range, the species are individually confined to a single range. In several of the ranges different species, or subspecies, are found at different heights.
Distribution chart
| range | Kilimanjaro | Meru | Kenya | Aberdares | Cherangani | Elgon | Ruwenzori | Virunga | Mitumba |
|---|---|---|---|---|---|---|---|---|---|
| higher altitude | D. kilimanjari ssp. cottonii | D. keniodendron | D. keniodendron | D. elgonensis ssp. barbatipes | |||||
| intermediate altitude | D. kilimanjari ssp. kilimanjari | D. meruensis | D. keniensis | D. brassiciformis | D. cherangiensis ssp. dalei | D. elgonensis ssp. elgonensis | D. adnivalis (two subspecies) | D. eric-rosenii ssp. alticola | |
| lower altitude | D. johnstonii | D. battiscombei | D. battiscombei | D. cherangiensis ssp. cherangiensis | D. eric-rosenii ssp. eric-rosenii | D. eric-rosenii ssp. eric-rosenii | D. eric-rosenii ssp. eric-rosenii |
Evolution and adaptation
The mountains of centralCentral Africa
Central Africa is a core region of the African continent which includes Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, and Rwanda....
and eastern Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
are an almost ideal model system for studying speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
and adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
in plants. The mountains rise far above the surrounding plains and plateaus,
tall enough to reach above the tree line
forming "islands in the sky" or isolated habitats.
These predominantly volcanic peaks further simplify the model by their age and arrangement around the Lake Victoria
Lake Victoria
Lake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
basin and proximity to the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
.
The species found on Mount Kenya
Mount Kenya
Mount Kenya is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian , Nelion and Point Lenana . Mount Kenya is located in central Kenya, just south of the equator, around north-northeast of the capital Nairobi...
are by far the best model for altitudinal variation. Dendrosenecio keniodendron is the species which grows at the highest of altitudes, Dendrosenecio keniensis is found at the lower altitudes of the range where the species grows and Dendrosenecio battiscombei grows at the same altitudes as D. keniensis but in the wetter environments. The other mountains which are not tall enough to have a "big one at the top" have the two, one species for the drier land and one for the damper environments or just one because the environment is not so extreme. This simplification works extremely well as an introduction to the giant groundsel of East Africa with one exception, Kilimanjaro who has the one species that lives at the top and only one species that lives below; subspecies and varieties living in the moister environments.
Gridded Adaptive Speciation Studies: Each mountain has a vertical gradient of precipitation and temperature fluctuations.Mount Kilimanjaro
Mount Kilimanjaro
Kilimanjaro, with its three volcanic cones, Kibo, Mawenzi, and Shira, is a dormant volcano in Kilimanjaro National Park, Tanzania and the highest mountain in Africa at above sea level .-Geology:...
at 5,985 metres (19,640 ft), Mount Kenya
Mount Kenya
Mount Kenya is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian , Nelion and Point Lenana . Mount Kenya is located in central Kenya, just south of the equator, around north-northeast of the capital Nairobi...
at 5,198 metres (17,050 ft) and Ruwenzori at 5,109 metres (16,760 ft)) are the three tallest mountains in Africa; each tall enough to support altitude based layers of vegetative zones. Each mountain providing its own vertically placed array of isolated habitats.
- Located from 50 kilometres (31.1 mi) to 1000 kilometres (621.4 mi) around the equator, the environmental fluctuations occur as daily events of warm days and cold nights and are consistent throughout the year or as HedbergKarl Olov HedbergProf. Karl Olov Hedberg of Västeråsa botanist, taxonomist, author, professor of systematic botany at Uppsala University from 1970 to 1989 and an Editor of the Flora of Ethiopia; was updating the Umbelliferae manuscript when he died in 2007...
described this unique situation: "summer every day, winter every night". In addition to the simplified environmental variables, these mountains are easily described for biogeographic analysis as their age and arrangement around the Lake VictoriaLake VictoriaLake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....
basin make it easy to disentangle the effects of time and position.- Vegetation zones:
-
- In the altitudes between 3400 meters (11,000 feet) and 4500 meters (15,000 feet) some of the most extreme examples of adaptations can be found, which include:
- Massive leaf rosettes in which leaf development occurs in a large "apical budApical dominanceIn plant physiology, apical dominance is the phenomenon whereby the main central stem of the plant is dominant over other side stems; on a branch the main stem of the branch is further dominant over its own side branchlets....
" - Water storage in the pithPithPith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which store and transport nutrients throughout the plant. In eudicots, pith is located in the center of the stem. In monocots, it extends also into flowering stems and roots...
of the stem - Insulation of the stem by retaining withered and dead foliage
- Secretion and impoundment of ice-nucleating polysaccharidePolysaccharidePolysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
fluids (a natural anti-freeze) - NyctinasticNyctinastyNyctinasty is the circadian rhythmic nastic movement of higher plants in response to the onset of darkness. Examples are the closing of the petals of a flower at dusk and the sleep movements of the leaves of many legumes....
leaf movement (the leaves close when it gets cold)
- Massive leaf rosettes in which leaf development occurs in a large "apical bud
- In the altitudes between 3400 meters (11,000 feet) and 4500 meters (15,000 feet) some of the most extreme examples of adaptations can be found, which include:
-
- At altitudes below 3400 meters (12,000 feet)the daily temperature fluctuations are less extreme, the average daily temperature steadily increases, and the growth forms and ecology of the Dendroseneico reflect the increased influence of biotic factors (such as competition for light) over abiotic factorsAbiotic componentsIn biology and ecology, abiotic components are non-living chemical and physical factors in the environment which affect ecosystems. Abiotic phenomena underlie all of biology. Abiotic factors, while generally downplayed, can have enormous impact on ramonds evolution...
(such as nightly frost).
- At altitudes below 3400 meters (12,000 feet)the daily temperature fluctuations are less extreme, the average daily temperature steadily increases, and the growth forms and ecology of the Dendroseneico reflect the increased influence of biotic factors (such as competition for light) over abiotic factors
-
-
- 3400-3800 meters (11,000-12,000 feet): Given the name Afro-alpine region by HaumanLucien Leon HaumanLucien Leon Hauman-Merck was a botanist and an author who studied and collected plants in Eastern Africa.-External links:*Inter-American Institute of Agricultural Sciences, Asociación Latinoamericana de Fitotecnia, ....
in 1955. There is a sharp boundary at 3400 meters (3000 meters on the North side) that separates the forest from the lower alpine zone, the environment is a moorlandMoorlandMoorland or moor is a type of habitat, in the temperate grasslands, savannas, and shrublands biome, found in upland areas, characterised by low-growing vegetation on acidic soils and heavy fog...
(low growing vegetationon acidic soils) and it is here that the Dendrosenecio start to grow among the mountain and sedges.
- Dendrosenecio keniensisDendrosenecio keniensisDendrosenecio keniensis Dendrosenecio keniensis Dendrosenecio keniensis (syn. Senecio keniensis and S. brassica is one of the giant groundsels endemic the higher altitudes of Mount Kenya. It is in the family Asteraceae and the genus Dendrosenecio (previously a Senecio). Dendrosenecio keniodendron...
grows in this region on Mount KenyaMount KenyaMount Kenya is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian , Nelion and Point Lenana . Mount Kenya is located in central Kenya, just south of the equator, around north-northeast of the capital Nairobi...
. A variety or subspecies of Dendrosenecio johnstonii live within this altitude range on all three of the tallest mountains.
- 3800-4500 meters (12,000-15,000 ft): The upper moorlandMoorlandMoorland or moor is a type of habitat, in the temperate grasslands, savannas, and shrublands biome, found in upland areas, characterised by low-growing vegetation on acidic soils and heavy fog...
s; this is where most of the D. brassica make their homes on all three of the mountains, living with tough dwarf shrubsSclerophyllSclerophyll is the term for a type of vegetation that has hard leaves and short internodes . The word comes from the Greek sclero and phyllon ....
. - 4300-5000 meters (14,000-16,000 ft): Dendrosenecio woodlands, where each mountain has its own special variety. Dendrosenecio keniensis on Mount Kenya, Dendrosenecio kilimanjariDendrosenecio kilimanjariDendrosenecio kilimanjari is a giant groundsel found atop Mount Kilimanjaro in Africa. It was originally known as Senecio kilimanjari, but a recent botanical reclassification split off some species formerly in Senecio, putting it and various other species in the new genus Dendrosenecio. Both genera...
on Mount Kilimanjaro and other species each on their own mountain. - 4500 meters-peak (15,000 ft): Populations of Dendrosenecio start to dwindle. Mount Kenya has the least vegetation in its upper parts due to its freezing temperatures.
- 3400-3800 meters (11,000-12,000 feet): Given the name Afro-alpine region by Hauman
-
Dispersal and establishment:
| Kilimanjaro Dendrosenecio kilimanjari Dendrosenecio kilimanjari Dendrosenecio kilimanjari is a giant groundsel found atop Mount Kilimanjaro in Africa. It was originally known as Senecio kilimanjari, but a recent botanical reclassification split off some species formerly in Senecio, putting it and various other species in the new genus Dendrosenecio. Both genera... D. johnstonii Dendrosenecio johnstonii Dendrosenecio johnstonii, formerly Senecio johnstonii, is a 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... |
|||
| Aberdare Range Aberdare Range The Aberdare Range is a 160 km long mountain range of upland, north of Kenya's capital Nairobi with an average elevation of . It is located in west central Kenya, northeast of Naivasha and Gilgil and just south of the Equator... D. battiscombei Dendrosenecio battiscombei Dendrosenecio battiscombei is one of the giant groundsels that lives on the slopes of Mount Kenya and the Aberdare Range... D. brassiciformis Dendrosenecio brassiciformis Dendrosenecio brassiciformis is one of the East African giant groundsel, this one is endemic to the slopes of Aberdare Range and bearing fruit but once, and dying after... |
Mount Meru (Tanzania) Mount Meru (Tanzania) Mount Meru is an active stratovolcano located west of Mount Kilimanjaro in the nation of Tanzania. At a height of , it is visible from Mt Kilimanjaro on a clear day, and is the tenth highest mountain in Africa. Much of its bulk was lost about 8,000 years ago due to an eastward volcanic blast,... D. meruensis Dendrosenecio meruensis Dendrosenecio meruensis is one of the East African giant groundsel, this one is endemic to the slopes of Mount Meru. Once they were considered to be of the genus Senecio but since then have been reclassified into their own genus Dendrosenecio.... |
||
| Mount Kenya Mount Kenya Mount Kenya is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian , Nelion and Point Lenana . Mount Kenya is located in central Kenya, just south of the equator, around north-northeast of the capital Nairobi... D. keniodendron Dendrosenecio keniodendron 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 Afrotropic, including Dendrosenecio johnstoniioccurring on Mount Kilimanjaro, Mount Kenya,... D. keniensis Dendrosenecio keniensis Dendrosenecio keniensis Dendrosenecio keniensis Dendrosenecio keniensis (syn. Senecio keniensis and S. brassica is one of the giant groundsels endemic the higher altitudes of Mount Kenya. It is in the family Asteraceae and the genus Dendrosenecio (previously a Senecio). Dendrosenecio keniodendron... D. battiscombei Dendrosenecio battiscombei Dendrosenecio battiscombei is one of the giant groundsels that lives on the slopes of Mount Kenya and the Aberdare Range... |
Cherangani Hills Cherangani Hills Cherangani Hills, gently rolling slopes in the western highlands of Kenya, are one of Kenya's five main forests. The highlands, the large central plateau, is divided by the Mau Escarpment rising from the border with Tanzania up to the Cherangani Hills, fencing the plateau that rises to the slopes... D. cheranganiensis Dendrosenecio cheranganiensis Dendrosenecio cheranganiensis is one of the East African giant groundsel, this one endemic to the Cherangani Hills. Once it was a genus of Senecio but has recently been reclassified as a Dendrosenecio.-Description:... |
Mount Elgon Mount Elgon Mount Elgon is an extinct shield volcano on the border of Uganda and Kenya, north of Kisumu and west of Kitale.- Physical features :It is the oldest and largest solitary volcano in East Africa, covering an area of around 3500 km².... D. elgonensis Dendrosenecio elgonensis 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 Senecio genus but recently have been reclassified to their own genus Dendrosenecio.-Description:... |
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| Aberdare Range Aberdare Range The Aberdare Range is a 160 km long mountain range of upland, north of Kenya's capital Nairobi with an average elevation of . It is located in west central Kenya, northeast of Naivasha and Gilgil and just south of the Equator... D. keniodendron Dendrosenecio keniodendron 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 Afrotropic, including Dendrosenecio johnstoniioccurring on Mount Kilimanjaro, Mount Kenya,... |
Virunga Mountains Virunga Mountains The Virunga Mountains are a chain of volcanoes in East Africa, along the northern border of Rwanda, the Democratic Republic of the Congo and Uganda. The mountain range is a branch of the Albertine Rift, a part of the Great Rift Valley. They are located between Lake Edward and Lake Kivu... D. erici-rosenii Dendrosenecio erici-rosenii Dendrosenecio erici-rosenii one of the East African giant groundsel and this one can be found on the Ruwenzori Mountains, Virunga Mountains and the Mitumba Mountains. A species of the genus Dendrosenecio and is also a collection of reclassified Senecio species.-Description:Dendrosenecio... |
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| Mitumba Mountains Mitumba Mountains The Mitumba Mountain range stretches along the Western Rift Valley in Burundi and Eastern Congo , west of lake Tanganyika. The two main peaks, Mount Kahuzi and Mount Biéga are extinct volcanoes.-References:... D. erici-rosenii Dendrosenecio erici-rosenii Dendrosenecio erici-rosenii one of the East African giant groundsel and this one can be found on the Ruwenzori Mountains, Virunga Mountains and the Mitumba Mountains. A species of the genus Dendrosenecio and is also a collection of reclassified Senecio species.-Description:Dendrosenecio... |
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| Ruwenzori Mountains D. erici-rosenii Dendrosenecio erici-rosenii Dendrosenecio erici-rosenii one of the East African giant groundsel and this one can be found on the Ruwenzori Mountains, Virunga Mountains and the Mitumba Mountains. A species of the genus Dendrosenecio and is also a collection of reclassified Senecio species.-Description:Dendrosenecio... D. adnivalis Dendrosenecio adnivalis Dendrosenecio adnivalis is one of the giant groundsels of the mountains of Eastern Africa. D. adnivalis grows on the Ruwenzori Mountainsand on the Virunga Mountainsin Uganda and the Democratic Republic of Congo.... |
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- BiogeographicBiogeographyBiogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
interpretation of the molecular phylogeny suggests that in the most recent one millionMillionOne million or one thousand thousand, is the natural number following 999,999 and preceding 1,000,001. The word is derived from the early Italian millione , from mille, "thousand", plus the augmentative suffix -one.In scientific notation, it is written as or just 106...
years, the first giant senecios established themselves at higher elevations of Mount KilimanjaroMount KilimanjaroKilimanjaro, with its three volcanic cones, Kibo, Mawenzi, and Shira, is a dormant volcano in Kilimanjaro National Park, Tanzania and the highest mountain in Africa at above sea level .-Geology:...
and became the species D. kilimanjariDendrosenecio kilimanjariDendrosenecio kilimanjari is a giant groundsel found atop Mount Kilimanjaro in Africa. It was originally known as Senecio kilimanjari, but a recent botanical reclassification split off some species formerly in Senecio, putting it and various other species in the new genus Dendrosenecio. Both genera...
. As they moved down that mountain, adapting to live in the different environment at the lower altitudes of Mount Kilimanjaro, they became a new species, D. johnstoniiDendrosenecio johnstoniiDendrosenecio johnstonii, formerly Senecio johnstonii, is a 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...
. Some seeds found a way to Mount Meru and established themselves as the species D. meruensisDendrosenecio meruensisDendrosenecio meruensis is one of the East African giant groundsel, this one is endemic to the slopes of Mount Meru. Once they were considered to be of the genus Senecio but since then have been reclassified into their own genus Dendrosenecio....
, others found a way to get from Mount Kilamanjaro to the Aberdare RangeAberdare RangeThe Aberdare Range is a 160 km long mountain range of upland, north of Kenya's capital Nairobi with an average elevation of . It is located in west central Kenya, northeast of Naivasha and Gilgil and just south of the Equator...
and established themselves as D. battiscombeiDendrosenecio battiscombeiDendrosenecio battiscombei is one of the giant groundsels that lives on the slopes of Mount Kenya and the Aberdare Range...
. D. battiscombei migrated into the wet alpine habitat on the Aberdares resulted in the formation of the species D. brassiciformisDendrosenecio brassiciformisDendrosenecio brassiciformis is one of the East African giant groundsel, this one is endemic to the slopes of Aberdare Range and bearing fruit but once, and dying after...
. Dispersal from the Aberdares to Mount KenyaMount KenyaMount Kenya is the highest mountain in Kenya and the second-highest in Africa, after Kilimanjaro. The highest peaks of the mountain are Batian , Nelion and Point Lenana . Mount Kenya is located in central Kenya, just south of the equator, around north-northeast of the capital Nairobi...
established a second isolated population of D. battiscombei. Altitudinal speciation on Mount Kenya resulted in the formation of D. keniodendronDendrosenecio keniodendronDendrosenecio 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 Afrotropic, including Dendrosenecio johnstoniioccurring on Mount Kilimanjaro, Mount Kenya,...
and the "dwarf" D. keniensisDendrosenecio keniensisDendrosenecio keniensis Dendrosenecio keniensis Dendrosenecio keniensis (syn. Senecio keniensis and S. brassica is one of the giant groundsels endemic the higher altitudes of Mount Kenya. It is in the family Asteraceae and the genus Dendrosenecio (previously a Senecio). Dendrosenecio keniodendron...
. Dispersal from Mount Kenya back to the Aberdares established a second insular population of D. keniodendron. Dispersal from the Aberdares to the Cherangani HillsCherangani HillsCherangani Hills, gently rolling slopes in the western highlands of Kenya, are one of Kenya's five main forests. The highlands, the large central plateau, is divided by the Mau Escarpment rising from the border with Tanzania up to the Cherangani Hills, fencing the plateau that rises to the slopes...
established two subspecies of D. cheranganiensisDendrosenecio cheranganiensisDendrosenecio cheranganiensis is one of the East African giant groundsel, this one endemic to the Cherangani Hills. Once it was a genus of Senecio but has recently been reclassified as a Dendrosenecio.-Description:...
: D. cheranganiensis subsp. cheranganiensis and altitudinal (sub)speciation into the web alpine habitat resulted in D. cheranganiensis subsp. dalei. Dispersal from the Aberdares to Mount ElgonMount ElgonMount Elgon is an extinct shield volcano on the border of Uganda and Kenya, north of Kisumu and west of Kitale.- Physical features :It is the oldest and largest solitary volcano in East Africa, covering an area of around 3500 km²....
established D. elgonensisDendrosenecio elgonensisDendrosenecio 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 Senecio genus but recently have been reclassified to their own genus Dendrosenecio.-Description:...
which is a point where several subspecies diverge and disperse: from Mount Elgon to the Virunga MountainsVirunga MountainsThe Virunga Mountains are a chain of volcanoes in East Africa, along the northern border of Rwanda, the Democratic Republic of the Congo and Uganda. The mountain range is a branch of the Albertine Rift, a part of the Great Rift Valley. They are located between Lake Edward and Lake Kivu...
established D. erici-roseniiDendrosenecio erici-roseniiDendrosenecio erici-rosenii one of the East African giant groundsel and this one can be found on the Ruwenzori Mountains, Virunga Mountains and the Mitumba Mountains. A species of the genus Dendrosenecio and is also a collection of reclassified Senecio species.-Description:Dendrosenecio...
; from Mount Elgon to Mount Kahuzi (Mitumba MountainsMitumba MountainsThe Mitumba Mountain range stretches along the Western Rift Valley in Burundi and Eastern Congo , west of lake Tanganyika. The two main peaks, Mount Kahuzi and Mount Biéga are extinct volcanoes.-References:...
) established a second population of D. erici-rosenii and dispersal from the Virunga Mountains to the Ruwenzori Mountains established a third population.
Parallel evolution
The communities of giant Dendrosenecio and s found on these African mountains are an exceptional example of parallelParallel evolution
Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...
or convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
and repeated convergent evolution between these two groups; providing evidence that the unusual features of these plants are an evolutionary response to a challenging habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
and an environment
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....
which can be easily described for biogeographic
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
analysis.
Cytological uniformity
Little variation was found in molecular phylogenyMolecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...
among the 40 recorded giant senecio collections (40 accessions), yet as a group they differ significantly from Cineraria deltoidea
Cineraria deltoidea
Cineraria deltoidea is a perennial flowering plant of the family Asteraceae and the genus Cineraria who is also the closest known relative of the giant Dendrosenecio of East Africa.-Description:...
, the closest known relative.
The gametophytic
Gametophyte
A gametophyte is the haploid, multicellular phase of plants and algae that undergo alternation of generations, with each of its cells containing only a single set of chromosomes....
chromosome number (is the number of chromosomes in each cell) for the giant Dendrosenecio is n = 50, and for the giant lobelias (specifically Lobeliaceae
Lobeliaceae
Lobelioideae is a subfamily of the plant family Campanulaceae. It contains 32 genera, totalling about 1200 species. Some of the larger genera are Lobelia, Siphocampylus, Centropogon, Burmeistera and Cyanea....
, Lobelia
Lobelia
Lobelia is a genus of flowering plant comprising 360–400 species, with a subcosmopolitan distribution primarily in tropical to warm temperate regions of the world, a few species extending into cooler temperate regions...
subgenus Tupa
Lobelia tupa
Lobelia tupa is a species of Lobelia native to central Chile from Valparaíso south to Los Lagos regions....
section Rhynchopetalum it is n = 14. Only five of the 11 species of giant senecio and three of the 21 species of giant lobelia from eastern Africa remain uncounted. Although both groups are polyploid
Polyploidy
Polyploid is a term used to describe cells and organisms containing more than two paired sets of chromosomes. Most eukaryotic species are diploid, meaning they have two sets of chromosomes — one set inherited from each parent. However polyploidy is found in some organisms and is especially common...
, Dendrosenecio is presumed to be decaploid (ten sets; 10x) and the Lobelia more certainly tetraploid (four sets; 4x), their adaptive radiation
Adaptive radiation
In evolutionary biology, adaptive radiation is the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. Starting with a recent single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different...
s involved no further change in chromosome number. The cytological
Cell biology
Cell biology is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level...
uniformity within each group, while providing circumstantial evidence that they descended from a single ancestor and simplifying interpretations of cladistic analyses, provides neither positive nor negative support for a possible role of polyploidy in evolving the giant-rosette growth-form.