Senecio squalidus, known as Oxford ragwort,[6] is a flowering plant in the daisy familyAsteraceae. 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.
Senecio nebrodensis auct., non L. Senecio laciniatus Bertol.[2] Senecio rupestris Waldst. & Kit.[3] Senecio squalidus d'Urv. Senecio squalidus Willd. Senecio squalidus M.Bieb.[4] Jacobaea incisa C. Presl Senecio glaber Ucria Senecio incisus (C. Presl) C. Presl[5]
Descriptionedit
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.[7]
Oxford ragwort is a short-lived perennial, a biennial, or a winter annual and grows in a branched straggling form to between 1.5 feet (0.5 m) and 3.3 feet (1 m) depending on conditions. S. squalidus prefers dry, disturbed places, cultivated and waste ground, walls and railway banks.[3][8] It flowers from March[9] to December[8]
and reproduces from seed.[3]
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)[3][8] with the exception that their lobes are more widely spaced.[10]
Inflorescence
S. squalidus has larger capitula than Senecio jacobaea and a more spreading habit.[9] Yellow capitula of 10-14 petals in loose clusters. They are pollinated by insects. Ray corollas .3 inches (8 mm) to .6 inches (15 mm) long, .08 inches (2 mm) to .16 inches (4 mm) wide.[8]
Oxford ragwort is self-incompatible and needs pollen from other plants with different self-incompatibility alleles;[11]
[12][13] its own flower possess a stigma with characteristics of both the “dry” and “wet” types.[14]
Each pollinated Oxford ragwort floret matures into a bell to cylindrical shaped indehiscent achene, the shallowly ribbed fruit is light brown in colour and .06 inches (1.5 mm) to .12 inches (3 mm) long.[8] Each plant can produce approximately 10,000 fruits during the year.[15]
Mature capitulum
S. squalidus developing capitula.
Leaves and stalks of S. squalidus.
Capitula at different stages of development
As a Senecio and a diploidSenecio 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.[16]
Carl Linnaeus first described Senecio squalidus[20] 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.[18]
James Edward Smith officially identified the escaped Oxford ragwort with its formal name Senecio squalidus in 1800.[18]
The vortex of air following the express train carries the fruits in its wake. I have seen them enter a railway-carriage window near Oxford and remain suspended in the air in the compartment until they found an exit at Tilehurst.
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.[9]
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:
The origin of Senecio vulgaris var. hibernicus Syme was determined to be an introgression of Senecio squalidus into Senecio vulgaris subsp vulgaris
The suggestion that S. squalidus is actually a hybrid of two other Sicilian Senecio: S. aethnensis Jan ex DC and S. chrysanthemifoliusPoir.[18]
Distributionedit
Senecio squalidus grows on scree in mountainous regions of native range,[3] and earned its common name Oxford ragwort for its willingness and ability to grow in similar habitat elsewhere in the world.[18]
^ abcdeBrickfields Country Park (24 December 2007). "Oxford Ragwort - Senecio squalidus". Ask Brickfields Country Park a question. Retrieved 14 February 2008.
^ abcdPeter Llewellyn (23 August 2004). "Senecio squalidus Oxford ragwort". Wild Flowers of the British Isles. Wild Flower Society. Retrieved 12 February 2008.
^Hiscock, S.J. (2000). "Genetic control of self-incompatibility in Senecio squalidus L. (Asteraceae): a successful colonizing species". Heredity. 85 (1): 85, 10–19. doi:10.1046/j.1365-2540.2000.00692.x. PMID 10971686. S2CID 31529463.
^Hiscock, S.J. (2000). "Self-incompatibility in Senecio squalidus L. (Asteraceae)". Annals of Botany: 85, 181–190.
^Alexandra Allen. "Identification of genes regulating self-incompatibility in Senecio squalidus (Asteraceae)". University of Bristol, School of Biological Sciences. Retrieved 14 February 2008.
^Simon J. Hiscock; Karin Hoedemaekers; William E. Friedman; Hugh G. Dickinson (January 2002). "The stigma surface and pollen-stigma interactions in Senecio squalidus L. (Asteraceae) following cross (compatible) and self (incompatible) pollinations" (PDF). International Journal of Plant Sciences. 163 (1). University of Chicago, Hyde Park, Chicago: The University of Chicago Press: 1–16. doi:10.1086/324530. S2CID 84275629. 1058-5893/2002/16301-0001. Archived from the original (PDF) on 27 February 2020.
^ ab"Details for Senecio squalidus L." The National Biodiversity Network's Species Dictionary. Natural History Museum, London. 12 August 1994. Retrieved 14 February 2008.
^Peter Hollingsworth; Richard M. Bateman; Richard Gornall (1999). "Monophyly populations and species". Molecular systematics and plant evolution. CRC Press. pp. 504 pages. ISBN 0-7484-0908-4. Retrieved 23 April 2008.
^ abcdefgHarris, S.A. (2002). "Introduction of Oxford Ragwort, Senecio squalidus L. (Asteraceae), to the United Kingdom" (PDF). Watsonia. 24. Botanical Society of the British Isles: 31–43. Retrieved 14 February 2008.
^Chris Gliddon (12 February 1998). "Plant Invasion and Inter-Specific Hybridization". 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. Retrieved 14 February 2008.
^Global Biodiversity Information Facility. "Occurrence search Classification includes Species: Senecio squalidus ". Species Data. GBIF Data Portal. Retrieved 14 February 2008.
^"Senecio squalidus". Artículo de la Enciclopedia Libre Universal en Español (in Spanish). Retrieved 14 February 2008.
^ ab"Senecio squalidus L. (Oxford Ragwort)". BioImages: The Virtual Field-Guide (UK). Archived from the original on 7 September 2008. Retrieved 14 February 2008.
^Missouri Botanical Garden. "TROPICOS Web display Senecio squalidus L." Nomenclatural and Specimen Data Base. Missouri State Library. Retrieved 14 February 2008.
Further readingedit
Harris, S.A. (2002). "Introduction of Oxford Ragwort, Senecio squalidus L. (Asteraceae), to the United Kingdom" (PDF). Watsonia. 24. Botanical Society of the British Isles: 31–43. Retrieved 14 February 2008.
Abbot, R.J.; Lowe, A.J. (2003). "A new British species, Senecio eboracensis (Asteraceae), another hybrid derivative of S. vulgaris L. and S. squalidae L" (PDF). Watsonia. 24: 375–388. Archived from the original (PDF) on 27 September 2007. Retrieved 12 February 2008.
Hollingsworth, Peter; Richard M. Bateman; Richard Gornall (1999). "Monophyly populations and species". Molecular Systematics and Plant Evolution. CRC Press. pp. 504 pages. ISBN 0-7484-0908-4. Retrieved 23 April 2008.
External linksedit
Wikimedia Commons has media related to Senecio squalidus.
"Google maps Oxford to Tilehurst". Retrieved 14 February 2008.
Flora of North America. "31. Senecio squalidus Linnaeus". pp. Vol. 20 Page 548, 560, 561. Retrieved 14 February 2008.
Botanic Garden & Botanical Museum Berlin-Dahlem. "Details for: Senecio squalidus". Euro+Med PlantBase. Freie Universität Berlin. Retrieved 14 February 2008.
"Plants that Grow with Senecio squalidus - oxford ragwort". California Native Plant Link Exchange. Retrieved 14 February 2008.
Photographer: John Crellin (22 April 2006). "Senecio squalidus photographs for noncommercial use". Flowers that grow in North-Western Europe. Retrieved 14 February 2008.
"Senecio squalidus". Flora of Northern Ireland. National Museums and Galleries of Northern Ireland and Environment and Heritage Service. Retrieved 14 February 2008.
Diane Earl (26 September 2006). "Oxford Ragwort (Senecio squalidus)". Retrieved 14 February 2008.
Calflora. "Senecio squalidus L." Information on California plants for education, research and conservation. Retrieved 12 February 2008.