Senecio

Senecio is a genus of flowering plants in the daisy family (Asteraceae) that includes ragworts and groundsels.
Variously circumscribed taxonomically, the genus Senecio is one of the largest genera of flowering plants.
Description
Morphology
The flower heads are normally rayed 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. The only species which are trees are the species formerly belonging to Robinsonia occurring on the Juan Fernández Islands.
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
Many genera and the whole tribe are 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.
Genera that have been included are the following:
Aetheolaena
Culcitum
Hasteola
Iocenes B. Nord.
Lasiocephalus Willd. ex Schltdl.
Robinsonia
Synonyms
The following genera contain species that are or have been included within Senecio.
Antillanthus B. Nord.
Barkleyanthus H. Rob. & Brettell
Brachyglottis J. R. Forst. & G. Forst.
Canariothamnus B. Nord.
Curio P.V. Heath
Dauresia B. Nord. & Pelser
Dendrophorbium C. Jeffrey
Dendrosenecio (Hauman ex Hedberg) B. Nord. - Giant groundsels occurring in the high altitude areas of East Africa
Dorobaea Cass.
Dresslerothamnus H. Rob.
Elekmania B. Nord.
Herreranthus B. Nord.
Hubertia Bory
Jacobaea Mill.Leonis B. Nord.
Ligularia
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
Pseudojacobaea (Hook. f.) R. Mathur
Roldana La Llave
Sinosenecio B. Nord.
Synotis (C. B. Clarke) C. Jeffrey & Y. L. Chen
Telanthophora H. Rob. & Brettell
Tephroseris (Rchb.) Rchb.
Vendredia Baill.
Zemisia B. Nord.
Etymology
The scientific name, Senecio, means "old man".
Selected species
Senecio ampullaceus — Texas ragwort, Texas squaw-weed, Texas groundsel, clasping-leaf groundsel
Senecio angulatus L.f. — creeping groundsel
Senecio antisanae
Senecio arborescens
Senecio barbertonicus Klatt — succulent bush senecio
Senecio bigelovii — nodding groundsel
Senecio bosniacus G. Beck — Bosnian ragwort
Senecio brasiliensis (Spreng.) Less. — flor-das-almas
Senecio candicans — angel wings
Senecio cambrensis — Welsh groundsel, Welsh ragwort
Senecio crassissimus
Senecio elegans — purple groundsel
Senecio falklandicus
Senecio flaccidus Less. — Douglas senecio, threadleaf groundsel, threadleaf ragwort
Senecio gallicus Chaix — French groundsel
Senecio glaucus L. — Jaffa groundsel
Senecio howeanus
Senecio inaequidens — South African ragwort
Senecio iscoensis — Hieron.
Senecio keniophytum
Senecio lamarckianus
Senecio leucanthemifolius Poir. — coastal ragwort
Senecio madagascariensis — Madagascar ragwort
Senecio macroglossus — Natal ivy, wax ivy
Senecio neowbsteri Olympic Mountain groundsel
Senecio patagonicus
Senecio pauciradiatus
Senecio pulcher
Senecio sanmarcosensis
Senecio squalidus — Oxford ragwort
Senecio trapezuntinus
Senecio triangularis — arrowleaf groundsel
Senecio tropaeolifolius — false nasturtium
Senecio vaginatus
Senecio vernalis — eastern groundsel
Senecio viscosus — sticky ragwort
Senecio vulgaris — common groundsel, old-man-in-the-spring
Formerly in Senecio
Brachyglottis greyi (as S. greyi)
Pericallis × hybrida (as S. cruentus)
Rugelia nudicaulis — Rugels ragwort
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.
See also
Ragwort Control Act 2003
References
External links
Asteraceae genera
Taxa named by Carl Linnaeus