Senecio

Description

Morphology

The flower heads are often rayed (though the type species Senecio vulgaris does not have ray florets), with the heads borne in branched clusters, and usually completely yellow, but green, purple, white and blue flowers are known as well.

In its current circumscription, the genus contains species that are annual or perennial herbs, shrubs, small trees, aquatics or climbers.

Chemistry

Pyrrolizidine alkaloids are found in all Senecio species. These alkaloids serve as a natural biocides to deter or even kill animals that would eat them. Livestock generally do not find them palatable. Senecio species are used as food plants by the larvae of some Lepidoptera species that have developed tolerance for these alkaloids.

Taxonomy

The traditional circumscription of Senecio is artificial, being polyphyletic, even in its new circumscription which is based on genetic data. Despite the separation of many species into other genera, the genus still contains species and is one of the largest genera of flowering plants.

As no morphological synapomorphies are known to determine which species belong to the genus or not, no exact species number is known. The genus has an almost worldwide distribution and evolved in the mid- to late Miocene.

Phylogeny

As of 2007, many genera and the whole tribe were in need of revision. Many species currently placed in the genus need to be transferred to other or new genera, and others have been retransferred to Senecio. In its new delimitation the genus is still not monophyletic.

The following genera are currently accepted by Plants of the World Online, and contain species that are or have been included within Senecio.

• Aetheolaena Cass.
• Antillanthus B.Nord.
• Barkleyanthus H.Rob. & Brettell
• Bethencourtia Choisy (synonym Canariothamnus B.Nord.)
• Brachyglottis J.R.Forst. & G.Forst.{{cite journal | access-date =2008-04-10 | archive-date =2010-08-16 | archive-url =https://web.archive.org/web/20100816050902/http://www.nzjf.org/free_issues/NZJF31_3_1986/8B94A164-BF7A-4A5B-A45B-3ACE982D0C7C.pdf | url-status =dead
• Curio P.V.Heath
• Dauresia B.Nord. & Pelser
• Dendrophorbium C.Jeffrey
• Dendrosenecio (Hauman ex Hedberg) B.Nord. - Giant groundsels native to high-elevation areas of East Africa
• Dorobaea Cass.
• Dresslerothamnus H.Rob.
• Elekmania B.Nord.
• Hasteola Raf.
• Herreranthus B.Nord.
• Hubertia Bory
• Iocenes B.Nord.
• Jacobaea Mill.
• Leonis B.Nord.
• Ligularia Cass.
• Lundinia B.Nord.
• Mesogramma DC.
• Monticalia C.Jeffrey
• Nelsonianthus H.Rob. & Brettell
• Nesampelos B.Nord., nom. inval.
• Oldfeltia B.Nord. & Lundin
• Packera Á.Löve & D.Löve
• Pentacalia Cass.
• Pippenalia McVaugh
• Pittocaulon H.Rob. & Brettell
• Pojarkovia Askerova
• Psacaliopsis H.Rob. & Brettell
• Pseudogynoxys (Greenm.) Cabrera
• Robinsonia DC. (synonym Vendredia Baill.)
• Roldana La Llave
• Sinosenecio B.Nord.
• Synotis (C.B.Clarke) C.Jeffrey & Y.L.Chen
• Telanthophora H.Rob. & Brettell
• Tephroseris (Rchb.) Rchb.
• Zemisia B.Nord.{{cite web | access-date = 2008-02-27 | author-link = Germplasm Resources Information Network

Etymology

The scientific name Senecio derives from the latin 'senex' which means "old man".

Selected species

Main article: List of Senecio species

• Senecio ampullaceus Hook. — Texas ragwort, Texas squaw-weed, Texas groundsel, clasping-leaf groundsel{{cite web | access-date = 2008-04-10
• Senecio angulatus L.f. — creeping groundsel
• Senecio antisanae Benth.
• Senecio arborescens
• Senecio barbertonicus Klatt — succulent bush senecio
• Senecio bigelovii A.Gray — nodding groundsel
• Senecio brasiliensis (Spreng.) Less. — flor-das-almas
• Senecio cambrensis Rosser — Welsh groundsel, Welsh ragwort
• Senecio candicans Wall. ex DC. — angel wings
• Senecio casapaltensis Ball (synonym Senecio sanmarcosensis H.Beltrán)
• Senecio crassissimus Humbert
• Senecio decaryi Humbert — Madagascar senecio
• Senecio elegans L. — purple groundsel
• Senecio falklandicus Hook.f.
• Senecio flaccidus Less. — Douglas senecio, threadleaf groundsel, threadleaf ragwort
• Senecio gallicus Vill. ex Chaix — French groundsel
• Senecio glaucus L. — Jaffa groundsel
• Senecio howeanus Belcher
• Senecio inaequidens DC. — South African ragwort
• Senecio iscoensis Hieron.
• Senecio keniophytum R.E.Fr.
• Senecio lamarckianus Bullock
• Senecio leucanthemifolius Poir. — coastal ragwort
• Senecio macroglossus DC. — Natal ivy, wax ivy
• Senecio madagascariensis Poir. — Madagascar ragwort
• Senecio neowbsteri S.F.Blake – Olympic Mountain groundsel
• Senecio oxyriifolius DC. (synonym Senecio tropaeolifolius) — false nasturtium
• Senecio patagonicus Hook. & Arn.
• Senecio pauciradiatus Belcher
• Senecio pokohinuensis (de Lange & B.G.Murray) de Lange — Mokohinau groundsel
• Senecio pulcher Hook. & Arn.
• Senecio scandens Buch.-Ham. ex D.Don — climbing Senecio
• Senecio squalidus L. — Oxford ragwort
• Senecio triangularis Hook. — arrowleaf groundsel
• Senecio vaginatus Hook. & Arn.
• Senecio vernalis Waldst. & Kit. — eastern groundsel
• Senecio viscosus L. — sticky ragwort
• Senecio vulgaris L. — common groundsel, old-man-in-the-spring

Formerly in Senecio (partial list)

• Brachyglottis greyi (as S. greyi)
• Jacobaea vulgaris (common ragwort; as S. jacobaea)
• Pericallis × hybrida (as S. cruentus)
• Rugelia nudicaulis — Rugels ragwort
• Telanthophora grandifolia (Less.) H.Rob. & Brettell (as S. grandifolius Less.)
• Tephroseris papposa (Rchb.) Schur (as S. papposus)

Distribution

The genus Senecio is distributed almost worldwide. It is one of the few genera occurring in all five regions with a Mediterranean climate. Furthermore, species are found in mountainous regions, including tropical alpine-like areas.

References

References

1. "''Senecio'' L.". [[Royal Botanic Gardens, Kew]].
2. (2013-06-10). "The fate of Robinsonia (Asteraceae): sunk in Senecio, but still monophyletic?". Phytotaxa.
3. Taylor, Ronald J.. (1994). "Sagebrush Country: A Wildflower Sanctuary". Mountain Press Pub. Co.
4. (August 2008). "A Biosystematic Study of the Jacobaea maritima Group (Asteraceae, Senecioneae) in the Central Mediterranean Area". Taxon.
5. (2004). "History and concepts of big plant genera". [[Taxon (journal).
6. (2010-05-01). "Patterns and causes of incongruence between plastid and nuclear Senecioneae (Asteraceae) phylogenies". American Journal of Botany.
7. (2007). "An ITS Phylogeny of Tribe Senecioneae (Asteraceae) and a New Delimitation of Senecio L". Taxon.