Senecio eboracensis

Taxobox
name = "Senecio eboracensis"
regnum = Plantae
divisio = Magnoliophyta
classis = Magnoliopsida
ordo = Asterales
familia = Asteraceae
tribus = Senecioneae
genus = "Senecio"
species = "S. eboracensis"
binomial = "Senecio eboracensis"
binomial_authority = Abbott & Lowecite web
url = http://ww2.bgbm.org/EuroPlusMed/PTaxonDetail.asp?NameCache=Senecio eboracensis&PTRefFk=7000000
title = Details for: "Senecio eboracensis"
accessdate = 2008-02-12
author = Botanic Garden and Botanical Museum Berlin-Dahlem
authorlink = Botanical Garden in Berlin
format = HTML
work = Euro+Med PlantBase
publisher =

---

range_map_width = 240px
range_map_caption = Range of "Senecio eboracensis" in Great Britain.

York groundsel or York radiate groundsel, formally named "Senecio eboracensis", is a self-pollinating hybrid species of ragwortcite journal
title = A new British species, "Senecio eboracensis" (Asteraceae), another hybrid derivative of "S. vulgaris" L. and "S. squalidae" L.
url = http://www.watsonia.org.uk/Vol24p375.pdf
format = PDF
journal = Watsonia
last = Abbot
first = R.J.
coauthors = Lowe, A.J.
year = 2003
volume = 24
pages = pp. 375–388
accessdate = 2007-07-15 ] and one of only six new plants to be discovered in either the United Kingdom or North America in the last 100 years.cite web
url = http://education.guardian.co.uk/higher/news/story/0,,899255,00.html
title = Blooming unexpected
accessdate = 2008-02-13
author = Martin Wainwright
authorlink = The Guardian
date = 2003-02-20
format = HTML
work = Education Guardian
publisher = The Guardian] 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 happily 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.cite journal
title = Reproductive isolation of a new hybrid species, "Senecio eboracensis" Abbott & Lowe (Asteraceae)
url = http://www.nature.com/hdy/journal/v92/n5/full/6800432a.html
journal = Heredity
last = Lowe
first = A.J.
coauthors = Abbott, R.J.
year = 2004
date = May
volume = 92
issue = 5
pages = pp. 386–395
accessdate = 2007-07-15
doi = 10.1038/sj.hdy.6800432 ]

Description

York radiate groundsel is a deciduous annual plant that sets its seed within the 3 months that it takes this plant to mature from germination to the upwards of convert|16|in|cm|lk=on 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.

:Leaves and stems"S. eboraccensis" have large many lobed leaves divided into slender segments, the not reaching the midrib. The stems are mostly erect to ascending with an occasional horizontal base section up to convert|2|in|cm|lk=on 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 convert|7|in|cm|lk=on x convert|3.5|in|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 especially when compared to its Common ragwort parent. The flower-head, found at the tips of the plants (apical) appearing in clusters (an inflorescence) is usually comprised of 3-7 florets in a grouped corymb; at first dense and leafy but eventually less dense with peduncles convert|.2|in|cm|lk=on to convert|.79|in|cm which get longer when fruiting (up to convert|1|in|cm). The flower-head is broadly cylindrical (convert|.4|in|mm|lk=on x convert|.16|in|mm, 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 (convert|.2|in|mm to convert|.24|in|mm long and convert|.059|in|mm 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.

:SeedsThe umbrella-like achenes can be convert|.1|in|mm|lk=on to convert|.14|in|mm|lk=on 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 Eboracum, the classical name of , 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 York, England.

One of the parents "Senecio vulgaris" is a native to the areacite web
url = http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?33708
title = Taxon: "Senecio vulgaris" L.
accessdate = 2008-01-27
author = Germplasm Resources Information Network (GRIN)
authorlink = Germplasm Resources Information Network
date = 2007-05-04
format = HTML
work = Taxonomy for Plants
publisher = USDA, ARS, National Genetic Resources Program, National Germplasm Resources Laboratory, Beltsville, Maryland ] 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.cite web
url = http://www.bio.bris.ac.uk/research/plantrepro/oxford_ragwort.html
title = The Oxford Ragwort Story
accessdate = 2008-02-13
author = Plant reproduction and speciation group, University of Bristol
authorlink = University of Bristol
format = HTML
publisher = University of Bristol, School of Biological Sciences]

Evolution

A newcomer to the plant world, "York groundsel" has been used as an example to support Darwin-like evolutioncite web
url = http://www.timesonline.co.uk/tol/news/uk/article884624.ece
title = Scruffy little weed shows Darwin was right as evolution moves on
accessdate = 2008-02-13
author = Anthony Browne, Environment Editor, New York Times Online
authorlink = New York Times
date = 2003-02-20
format = HTML
publisher = New York Times] and also as evidence of the opposing theory of creationismcite web
url = http://www.answersingenesis.org/creation/v25/i3/newweed.asp
title = A new weed species—does it prove Creation wrong?
accessdate = 2008-02-13
author = Philip Bell, B.Sc.(Hons.), P.G.C.E., C.Biol. M.I.Biol.
authorlink = Answers in Genesis
year = 2003
month = June
format = HTML
work = Creation Archive
publisher = Answers in Genesis
pages = Volume 25 Issue 3] among groups who argue these theories. 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 1700s; 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"cite web
url = http://mobot.mobot.org/cgi-bin/search_pick?name=Senecio+vulgaris
title = TROPICOS Web display "Senecio vulgaris" L.
accessdate = 2008-02-01
author = Missouri Botanical Garden
authorlink = Missouri Botanical Garden
format = HTML
work = Nomenclatural and Specimen Data Base
publisher = Missouri State Library] ), 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.

References

ee also

*Common Cordgrass
*Welsh groundsel
*"Tragopogon miscellus"
*"Tragopogon mirus"
*"Raphanus sativus" x "Brassica rapa"

External links

*cite journal
url = http://www.nature.com/hdy/journal/v92/n5/fig_tab/6800432f2.html
title = FIGURE 2, Reproductive isolation of a new hybrid species, "Senecio eboracensis" Abbott & Lowe (Asteraceae)
accessdate = 2008-02-14
journal = Heredity
last = Lowe
first = A.J.
coauthors = Abbott, R.J.
year = 2004
date = May
volume = 92
issue = 5
pages = pp. 386–395
doi = 10.1038/sj.hdy.6800432
*cite book
last = Arnold
first = Michael L.
accessdate = 2008-02-14
title = Evolution Through Genetic Exchange
url = http://books.google.com/books?id=3U_7N0hNcqUC&pg=PA47&lpg=PA47&dq=senecio+eboracensis&source=web&ots=e2AXZ08Ahp&sig=WQrnYhGqEsbHRoczAFzopI6LhwQ
format = HTML
year = 2006
publisher = Oxford University Press
isbn = 0198570066
pages = pg 47 of 272 pages
*cite web
url = http://www.bsbi.org.uk/TPDB_species.pdf
title = Taxa covered by the Threatened Plants Database
accessdate = 2008-02-14
date = 2006-03-20
year = 20/3/2006
format = PDF
publisher = Botanical Studies of the British Isles
*cite journal
last = Adrian C Brennan, Stephen A Harris, and Simon J Hiscock
first = Department of Plant Sciences
authorlink = University of Oxford
coauthors = Adrian C Brennan, Stephen A Harris, and Simon J Hiscock
title = The population genetics of sporophytic self-incompatibility in Senecio squalidus L. (Asteraceae): avoidance of mating constraints imposed by low S-allele number.
journal = Philosophical Transactions of the Royal Society
volume = 358
issue = 1434
pages = 1047–1050
publisher = Royal Society
location = Carlton House Terrace, London, England
date = 2003-06-29 | url = http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1693209&blobtype=pdf
doi = 10.1098/rstb.2003.1300
accessdate = 2008-02-14

Further reading

*cite journal
title = A new British species, "Senecio eboracensis" (Asteraceae), another hybrid derivative of "S. vulgaris" L. and "S. squalidae" L.
url = http://www.watsonia.org.uk/Vol24p375.pdf
format = PDF
journal = Watsonia
last = Abbot
first = R.J.
coauthors = Lowe, A.J.
year = 2003
volume = 24
pages = pp. 375–388
accessdate = 2008-02-12