Senecio squalidus explained

Senecio squalidus, known as Oxford ragwort, is a flowering plant 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. These habitats resemble its well drained natural rocky homeland. The plants have spread via the wind, rail and the activities of botanists. The travels of this short-lived perennial, biennial, or winter annual make it a good subject for studies of the evolution and ecology of flowering plants.

Description

Like all members of the family Asteraceae, Senecio squalidus has a composite flower head known as a capitulum. What look like single flowers are actually a cluster of florets, each petal or ligule being a flower, or floret, possessing its own stamen and capable of producing the specialized seed of the family Asteraceae, the parachute-like achene.[1]

Oxford ragwort is a short-lived perennial, a biennial, or a winter annual and grows in a branched straggling form to between 1.5feet and 3.3feet depending on conditions. S. squalidus prefers dry, disturbed places, cultivated and waste ground, walls and railway banks.[2] It flowers from March[3] to December[2] and reproduces from seed.

Leaves and stems: S. squalidus leaves are alternate, glossy, almost hairless and variable in form from deeply pinnately lobed to undivided with only the lower leaves being stalked. Stems and leaves resemble those of the common groundsel (Senecio vulgaris)[2] with the exception that their lobes are more widely spaced.[4]
Inflorescence: S. squalidus has larger capitula than Senecio jacobaea and a more spreading habit.[3] Yellow capitula of 10-14 petals in loose clusters. They are pollinated by insects. Ray corollas 0.3inches to 0.6inches long, 0.08inches to 0.16inches wide.[2]

Oxford ragwort is self-incompatible and needs pollen from other plants with different self-incompatibility alleles;[5] [6] [7] its own flower possess a stigma with characteristics of both the “dry” and “wet” types.[8]

The fruiting heads are often nodding.

Seeds: Each pollinated Oxford ragwort floret matures into a bell to cylindrical shaped indehiscent achene, the shallowly ribbed fruit is light brown in colour and 0.06inches to 0.12inches long.[2] Each plant can produce approximately 10,000 fruits during the year.[9]

As a Senecio and a diploid Senecio squalidus is part of a species group along with S. flavus, S. gallicus, S. glaucus and S. vernalis, which are widespread geographically and interesting for the study of genetic differences in relation to the environment and plant evolution.[10]

History

This Senecio was introduced into Britain via Francesco Cupani and William Sherard in the years of their visit 1700, 1701 and 1702 from Sicily[11] where it lives as a native on volcanic ash[9] to the Duchess of Beaufort's garden at Badminton. Later a transfer of the plant material to the Oxford Botanic Garden by the "Horti Praefectus" Jacob Bobart the Younger took place before his death in 1719,[12] providing perhaps a good indication of when this species of ragwort and other invasive species might have "escaped" and started to make their home in the greater British Isles. The Sicilian ragwort escaped into the wild and grew in the stonework of Oxford colleges (with the specific mention of the Bodleian Library[3]) and many of the stone walls around the city of Oxford. This gave the plant its common name, "Oxford Ragwort".[13]

Carl Linnaeus first described Senecio squalidus[14] in 1753, although there is a dispute as to whether the material came from the Botanic Garden or from walls in the city; the taxonomy for this species is further complicated by the existence of species with a similar morphology in continental Europe.[12]

James Edward Smith officially identified the escaped Oxford ragwort with its formal name Senecio squalidus in 1800.[12]

During the Industrial Revolution, Oxford became connected to the railway system and the plant gained a new habitat in the railway lines clinker beds, gradually spreading via the railway to other parts of the country. The process was accelerated by the movement of the trains [13] and the limestone ballast that provides a well-drained medium which is an adequate replica of the lava-soils of its native home in Sicily.[12] [15]

During the 20th century it continued to spread along railway lines and found a liking for waste places and bombed sites after World War II which have a lot in common with the volcanic regions of its home.[3]

Recently, this and other Senecio species and their differing tastes for self-incompatibility and self-compatibility have been the subject of study for the purposes of understanding the evolution of plant species as the genus finds new homes and pollen partners throughout the world:

Distribution

Senecio squalidus grows on scree in mountainous regions of native range, and earned its common name Oxford ragwort for its willingness and ability to grow in similar habitat elsewhere in the world.[12]

Native[16]

Senecio squalidus is considered to be a native of New Brunswick and Nova Scotia, Canada by the USDA Natural Resources Conservation Service while the same USDA other resource Germplasm Resources Information Network considers it to be native to Austria, Czech Republic, Slovakia, Germany, Switzerland, Albania, Bulgaria, Greece, Crete, Italy, Sardinia, Sicily, Romania, Bosnia and Herzegovina, Croatia, Montenegro, North Macedonia, Serbia, Slovenia.Current[17] [18]

Africa

Northern Africa: Morocco

America

North America: New Brunswick, Nova Scotia, British Columbia, California

Europe

Northern Europe: Denmark, Germany, Republic of Ireland, Netherlands, Norway, Sweden, United Kingdom

Middle Europe: Austria, Czech Republic, Hungary, Slovakia, Switzerland

East Europe: Poland,

Southeastern Europe: Albania, Bosnia and Herzegovina, Bulgaria

Southwestern Europe: France, Spain

South Europe: Croatia, Crete, Greece, Italy, North Macedonia, Romania, Sardinia, Serbia, Sicily, Slovenia

Range Maps

Predators

S. squalidus is a food plant for some insects, for example:

Flies

Gall flies (Diptera: Tephritidae):

Fungi

Most Senecio, including S. squalidus are susceptible to rust and other fungus and mildews:[19]

Rust fungus Uredinales

White rust Peronosporales

Sac fungus Ascochyta, Pezizomycetes

Powdery Mildew Erysiphales

Synonyms and misapplied names

Misapplied names:

Further reading

External links

Notes and References

  1. Web site: Asteraceae (Compositae) . 2008-02-14 . Dr. Gerald (Gerry) Carr, University of Hawaii, Botany Department . University of Hawaii . Vascular Plant Family Systematic Index.
  2. Web site: Oxford Ragwort - Senecio squalidus . 2008-02-14 . Brickfields Country Park . 2007-12-24 . Ask Brickfields Country Park a question.
  3. Web site: Senecio squalidus Oxford ragwort . 2008-02-12 . Peter Llewellyn . 23 August 2004 . Wild Flowers of the British Isles . Wild Flower Society.
  4. Web site: Identification of injurious weeds . 2008-02-15 . Department for Environment, Food and Rural Affairs . Department for Environment, Food and Rural Affairs . 2000-03-07 . Farming: wildlife and plants . United Kingdom Government.
  5. Hiscock . S.J. . Genetic control of self-incompatibility in Senecio squalidus L. (Asteraceae): a successful colonizing species . . 1. 85, 10–19. 10971686 . 2000 . 85. 10.1046/j.1365-2540.2000.00692.x . 31529463 .
  6. Hiscock . S.J. . Self-incompatibility in Senecio squalidus L. (Asteraceae) . 2000 . Annals of Botany . 85, 181–190.
  7. Web site: Identification of genes regulating self-incompatibility in Senecio squalidus (Asteraceae). . 2008-02-14 . Alexandra Allen . University of Bristol . University of Bristol, School of Biological Sciences .
  8. Simon J. Hiscock . Karin Hoedemaekers . William E. Friedman . Hugh G. Dickinson . The stigma surface and pollen-stigma interactions in Senecio squalidus L. (Asteraceae) following cross (compatible) and self (incompatible) pollinations . International Journal of Plant Sciences . 163 . 1 . 1–16 . . University of Chicago, Hyde Park, Chicago . January 2002 . 10.1086/324530 . 84275629 . 1058-5893/2002/16301-0001 . https://web.archive.org/web/20200227071915/https://pdfs.semanticscholar.org/db85/356c3edc723f39faad28ee7af49e5f54cffc.pdf . dead . 2020-02-27 .
  9. Web site: Details for Senecio squalidus L. . 2008-02-14 . 1994-08-12 . The National Biodiversity Network's Species Dictionary . Natural History Museum, London.
  10. Book: Peter Hollingsworth . Richard M. Bateman . Richard Gornall . Molecular systematics and plant evolution . 2008-04-23 . 1999 . . 0-7484-0908-4 . 504 pages . Monophyly populations and species . https://books.google.com/books?id=SVKN8V1cGg4C&pg=PA171.
  11. Web site: Monti Rossi . 2008-02-15 . University of Catania . University of Catania . it.
  12. Harris . S.A. . Botanical Society of the British Isles . Introduction of Oxford Ragwort, Senecio squalidus L. (Asteraceae), to the United Kingdom . . 24 . 31–43 . Botanical Society of the British Isles . 2002 . 2008-02-14 .
  13. Web site: The Oxford Ragwort Story . 2008-02-13 . Plant reproduction and speciation group, University of Bristol . University of Bristol . University of Bristol, School of Biological Sciences . 11 April 2009 . https://web.archive.org/web/20090411222925/http://www.bio.bris.ac.uk/research/plantrepro/oxford_ragwort.html . dead .
  14. Web site: Senecio squalidus L. . 2008-02-14 . Swedish Museum of Natural History . Swedish Museum of Natural History . 2003-08-20 . Linnean herbarium (S-LINN) .
  15. Web site: Plant Invasion and Inter-Specific Hybridization . 2008-02-14 . Chris Gliddon . United Nations Environment Programme . 1998-02-12 . The impact of hybrids between genetically modified crop plants and their related species: biological models and theoretical perspectives . Guide to Risk Assessment and Biosafety in Biotechnology, GRABB, United Nations Environment Programme.
  16. Web site: PLANTS Profile, Nativity of Senecio squalidus L. . 2008-02-14 . Natural Resources Conservation Service (NRCS) . Natural Resources Conservation Service . The PLANTS Database . .
  17. Web site: Occurrence search Classification includes Species: Senecio squalidus . 2008-02-14 . Global Biodiversity Information Facility . Global Biodiversity Information Facility . Species Data . GBIF Data Portal.
  18. Web site: Senecio squalidus . 2008-02-14 . es . Artículo de la Enciclopedia Libre Universal en Español.
  19. Web site: Senecio squalidus L. (Oxford Ragwort) . 2008-02-14 . BioImages: The Virtual Field-Guide (UK) . dead . https://web.archive.org/web/20080907222712/http://www.bioimages.org.uk/HTML/T606.HTM . 2008-09-07 .
  20. Web site: TROPICOS Web display Senecio squalidus L. . 2008-02-14 . Missouri Botanical Garden . Missouri Botanical Garden . Nomenclatural and Specimen Data Base . Missouri State Library.

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