Senecio eboracensis
Encyclopedia
Senecio eboracensis, the York groundsel or York radiate groundsel, is a self-pollinating hybrid species
of ragwort
and one of only six new plants to be discovered in either the United Kingdom
or North America
in the last 100 years.
It was discovered in 1979 in York
, England
growing next to a parking lot and formally described in 2003. Like many of the Senecio
genus
it can be found growing in urban habitats
, such as disturbed earth and pavement cracks and this particular species only in York and between a railway and a parking lot.
annual plant
that sets its seed within the 3 months that it takes this plant to mature from germination to the upwards of 16 inches (40.6 cm) high adult plant. With pretty yellow daisy-like
flowers from its Sicilian parent (S. squalidus
) but also with the less-promiscuous habits of its native parent (S. vulgaris); this member of the Senecio
genus is morphologically distinct from related species.
S. eboraccensis have large many lobed leaves divided into slender segments, the clefts not reaching the midrib. The stem
s are mostly erect to ascending with an occasional horizontal base section up to 2 inches (5 cm) with 'adventitious roots' at base. The upper and lower leaves petiolate
and lobes appearing at quarter whole leaf lengths along the midrib. The upper leaves are generally more deeply lobed and in lobed pairs. Leaves on plants grown in fertile soils or in greenhouses can be much more luxurious and more highly dissected (or more finely divided into slender segments) up to 7 inches (17.8 cm) x 3.5 inches (9 cm) with lobes appearing at fifth whole leaf lengths along the midrib. The plants tip is usually acute with a very small tooth. Leaf edges throughout are dentate or sometimes divided into lobes.
York groundsel has showy flower-heads
especially when compared to its Common ragwort parent. The flower-head, found at the tips of the plants (apical) appearing in clusters (an inflorescence) usually consists of three to seven florets in a grouped corymb; at first dense and leafy but eventually less dense with peduncles 5 to 20 millimeters (0.2 to 0.8 in) which get longer when fruiting (up to 25 mm (1 in)). The flower-head is broadly cylindrical 10×4 millimeters (0.4×0.16 in), becoming slightly bell shaped) when the bright yellow
ray florets open. Involucral bracts sparse (4-8), elongated (3.5–4 mm), usually without black tips. The floret ligules are narrow and long 5 to 7 millimeters (0.2 to 0.24 in) long and 1.5 millimeters (0.06 in) wide), occasionally becoming revolute. Like other Senecios, the 10-30 papilla occur stigmatically into pericarp; each usually with four-pored pollen, the grains in polar view 30-35 micrometers when fully expanded.
The umbrella-like achenes can be 2.5 to 3.5 millimeters (0.1 to 0.15 in) long, are straight and shallowly grooved; with hairless smooth ribs while the grooves are covered with hairs. Silky white pappus which readily detach from the fruit when ripe.
, the classical name of York, was chosen in the year 2000 to describe this tetraploid hybrid derivative informally named 'York radiate groundsel' at the time a formal description was made.
, England
.
One of the parents Senecio vulgaris is a native to the area
while the other parent Senecio squalidus
was introduced from Mount Etna
in Sicily
in 1690 to the Oxford Botanic Garden in Oxford
, England and was soon spreading happily along the railways and throughout the country.
. The refusal of S. eboracensis to breed back to its parents is the main point of contention between the rival parties.
The science of this plant is that it is a hybrid species
whose parents are the self-incompatible
and promiscuous Sicilian Senecio squalidus
(also known as Oxford ragwort) and the self-compatible and tenacious Senecio vulgaris (also known as Common groundsel). Like S. vulgaris, S. eboracensis is self-compatible, however, it shows little or no natural crossing with its parent species, and is therefore reproductively isolated
, indicating that strong breed barriers exist between this new hybrid and its parents.
It is thought to have resulted from a backcrossing
of the F1 hybrid
of its parents to S. vulgaris. S. vulgaris is native to Britain
, while S. squalidus was introduced from Sicily
in the early 18th century; therefore, S. eboracensis has speciated
from those two species within the last 300 years.
Other hybrids descended from the same two parents are known. Some are infertile, such as S. x baxteri. Other fertile hybrids are also known, including S. vulgaris var. hibernicus (which has been accepted as a synonym for S. vulgaris),
now common in Britain, and the allohexaploid
S. cambrensis
, which according to molecular evidence probably originated independently at least three times in different locations.
Morphological
and genetic
evidence support the status of S. eboracensis as separate from other known hybrids.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of ragwort
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...
and one of only six new plants to be discovered in either the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
or North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
in the last 100 years.
It was discovered in 1979 in York
York
York is a walled city, situated at the confluence of the Rivers Ouse and Foss in North Yorkshire, England. The city has a rich heritage and has provided the backdrop to major political events throughout much of its two millennia of existence...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
growing next to a parking lot and formally described in 2003. Like many of the 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...
genus
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...
it can be found growing in urban habitats
Urban geography
Urban geography is the study of areas which have a high concentration of buildings and infrastructure. These are areas where the majority of economic activities are in the secondary sector and tertiary sectors...
, such as disturbed earth and pavement cracks and this particular species only in York and between a railway and a parking lot.
Description
York radiate groundsel is a deciduousDeciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
annual plant
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...
that sets its seed within the 3 months that it takes this plant to mature from germination to the upwards of 16 inches (40.6 cm) high adult plant. With pretty yellow daisy-like
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...
flowers from its Sicilian parent (S. squalidus
Senecio squalidus
Oxford Ragwort , is a member of the Senecio genus in the daisy family Asteraceae. It is a yellow-flowered herbaceous plant, native to mountainous, rocky or volcanic areas, that has managed to find other homes on man-made and natural piles of rocks, war-ruined neighborhoods and even on stone walls...
) but also with the less-promiscuous habits of its native parent (S. vulgaris); this member of the 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...
genus is morphologically distinct from related species.
- Leaves and stems
S. eboraccensis have large many lobed leaves divided into slender segments, the clefts not reaching the midrib. The stem
Plant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
s are mostly erect to ascending with an occasional horizontal base section up to 2 inches (5 cm) with 'adventitious roots' at base. The upper and lower leaves petiolate
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
and lobes appearing at quarter whole leaf lengths along the midrib. The upper leaves are generally more deeply lobed and in lobed pairs. Leaves on plants grown in fertile soils or in greenhouses can be much more luxurious and more highly dissected (or more finely divided into slender segments) up to 7 inches (17.8 cm) x 3.5 inches (9 cm) with lobes appearing at fifth whole leaf lengths along the midrib. The plants tip is usually acute with a very small tooth. Leaf edges throughout are dentate or sometimes divided into lobes.
- Flowers
York groundsel has showy flower-heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
especially when compared to its Common ragwort parent. The flower-head, found at the tips of the plants (apical) appearing in clusters (an inflorescence) usually consists of three to seven florets in a grouped corymb; at first dense and leafy but eventually less dense with peduncles 5 to 20 millimeters (0.2 to 0.8 in) which get longer when fruiting (up to 25 mm (1 in)). The flower-head is broadly cylindrical 10×4 millimeters (0.4×0.16 in), becoming slightly bell shaped) when the bright yellow
Yellow
Yellow is the color evoked by light that stimulates both the L and M cone cells of the retina about equally, with no significant stimulation of the S cone cells. Light with a wavelength of 570–590 nm is yellow, as is light with a suitable mixture of red and green...
ray florets open. Involucral bracts sparse (4-8), elongated (3.5–4 mm), usually without black tips. The floret ligules are narrow and long 5 to 7 millimeters (0.2 to 0.24 in) long and 1.5 millimeters (0.06 in) wide), occasionally becoming revolute. Like other Senecios, the 10-30 papilla occur stigmatically into pericarp; each usually with four-pored pollen, the grains in polar view 30-35 micrometers when fully expanded.
- Seeds
The umbrella-like achenes can be 2.5 to 3.5 millimeters (0.1 to 0.15 in) long, are straight and shallowly grooved; with hairless smooth ribs while the grooves are covered with hairs. Silky white pappus which readily detach from the fruit when ripe.
Name
The word EboracumEboracum
Eboracum was a fort and city in Roman Britain. The settlement evolved into York, located in North Yorkshire, England.-Etymology:The first known recorded mention of Eboracum by name is dated circa 95-104 AD and is an address containing the Latin form of the settlement's name, "Eburaci", on a wooden...
, the classical name of York, was chosen in the year 2000 to describe this tetraploid hybrid derivative informally named 'York radiate groundsel' at the time a formal description was made.
Distribution
This groundsel occurs on disturbed ground, car park perimeters, pavement cracks and other urban/industrial sites; specifically in disturbed areas near to the railways in YorkYork
York is a walled city, situated at the confluence of the Rivers Ouse and Foss in North Yorkshire, England. The city has a rich heritage and has provided the backdrop to major political events throughout much of its two millennia of existence...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
.
One of the parents Senecio vulgaris is a native to the area
while the other parent Senecio squalidus
Senecio squalidus
Oxford Ragwort , is a member of the Senecio genus in the daisy family Asteraceae. It is a yellow-flowered herbaceous plant, native to mountainous, rocky or volcanic areas, that has managed to find other homes on man-made and natural piles of rocks, war-ruined neighborhoods and even on stone walls...
was introduced from Mount Etna
Mount Etna
Mount Etna is an active stratovolcano on the east coast of Sicily, close to Messina and Catania. It is the tallest active volcano in Europe, currently standing high, though this varies with summit eruptions; the mountain is 21 m higher than it was in 1981.. It is the highest mountain in...
in Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
in 1690 to the Oxford Botanic Garden in Oxford
Oxford
The city of Oxford is the county town of Oxfordshire, England. The city, made prominent by its medieval university, has a population of just under 165,000, with 153,900 living within the district boundary. It lies about 50 miles north-west of London. The rivers Cherwell and Thames run through...
, England and was soon spreading happily along the railways and throughout the country.
Evolution
A newcomer to the plant world, York groundsel has been used as an example to support macroevolutionMacroevolution
Macroevolution is evolution on a scale of separated gene pools. Macroevolutionary studies focus on change that occurs at or above the level of species, in contrast with microevolution, which refers to smaller evolutionary changes within a species or population.The process of speciation may fall...
. The refusal of S. eboracensis to breed back to its parents is the main point of contention between the rival parties.
The science of this plant is that it is a hybrid species
Hybrid speciation
Hybrid speciation is the process wherein hybridization between two different closely related species leads to a distinct phenotype. This phenotype in very rare cases can also be fitter than the parental lineage and as such natural selection may then favor these individuals. Eventually, if...
whose parents are the self-incompatible
Self-incompatibility in plants
Self-incompatibility is a general name for several genetic mechanisms in angiosperms, which prevent self-fertilization and thus encourage outcrossing...
and promiscuous Sicilian Senecio squalidus
Senecio squalidus
Oxford Ragwort , is a member of the Senecio genus in the daisy family Asteraceae. It is a yellow-flowered herbaceous plant, native to mountainous, rocky or volcanic areas, that has managed to find other homes on man-made and natural piles of rocks, war-ruined neighborhoods and even on stone walls...
(also known as Oxford ragwort) and the self-compatible and tenacious Senecio vulgaris (also known as Common groundsel). Like S. vulgaris, S. eboracensis is self-compatible, however, it shows little or no natural crossing with its parent species, and is therefore reproductively isolated
Reproductive isolation
The mechanisms of reproductive isolation or hybridization barriers are a collection of mechanisms, behaviors and physiological processes that prevent the members of two different species that cross or mate from producing offspring, or which ensure that any offspring that may be produced is not...
, indicating that strong breed barriers exist between this new hybrid and its parents.
It is thought to have resulted from a backcrossing
Backcrossing
Backcrossing is a crossing of a hybrid with one of its parents or an individual genetically similar to its parent, in order to achieve offspring with a genetic identity which is closer to that of the parent...
of the F1 hybrid
F1 hybrid
F1 hybrid is a term used in genetics and selective breeding. F1 stands for Filial 1, the first filial generation seeds/plants or animal offspring resulting from a cross mating of distinctly different parental types....
of its parents to S. vulgaris. S. vulgaris is native to Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, while S. squalidus was introduced from Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
in the early 18th century; therefore, S. eboracensis has speciated
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...
from those two species within the last 300 years.
Other hybrids descended from the same two parents are known. Some are infertile, such as S. x baxteri. Other fertile hybrids are also known, including S. vulgaris var. hibernicus (which has been accepted as a synonym for S. vulgaris),
now common in Britain, and the allohexaploid
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...
S. cambrensis
Senecio cambrensis
Senecio cambrensis is a flowering plant of the family Asteraceae. It is endemic to the United Kingdom and currently known only from North Wales...
, which according to molecular evidence probably originated independently at least three times in different locations.
Morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
and genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
evidence support the status of S. eboracensis as separate from other known hybrids.
See also
- Common CordgrassSpartina anglicaSpartina anglica is a species of cordgrass that originated in southern England in about 1870. It is an allotetraploid species derived from the hybrid Spartina × townsendii, which arose when the European native cordgrass Spartina maritima hybridised with the introduced American Spartina...
- Welsh groundselSenecio cambrensisSenecio cambrensis is a flowering plant of the family Asteraceae. It is endemic to the United Kingdom and currently known only from North Wales...
- Tragopogon miscellus
- Tragopogon mirus
- Raphanus sativusRaphanobrassicaBrassicoraphanus is the name for all the intergeneric hybrids between the genera Brassica and Raphanus . The name comes from the combination of the genus names...
x Brassica rapaRaphanobrassicaBrassicoraphanus is the name for all the intergeneric hybrids between the genera Brassica and Raphanus . The name comes from the combination of the genus names...