Senecio

Senecio is a genus of flowering plants in the daisy family (Asteraceae) that includes groundsels and some ragworts. Variously circumscribed taxonomically, the genus Senecio is one of the largest genera of flowering plants. Plants of the World Online currently accepts 1482 species.<ref name= powo/>

Description

Morphology

Senecio squalidus flowerheads have the yellow ray florets typical of many species

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.<ref>Template:Cite journal</ref>

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.<ref>Template:Cite book</ref> 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.<ref name="Senecioneae" /><ref>Template:Cite journal</ref> Despite the separation of many species into other genera, the genus still contains Template:Circa species and is one of the largest genera of flowering plants.<ref name="Frodin">Template:Cite journal</ref>

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<ref name="Senecioneae" /> and evolved in the mid- to late Miocene.<ref>Template:Cite journal</ref>

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.<ref name="Senecioneae" />

S. barbertonicus Succulent Bush Senecio

The following genera are currently accepted by Plants of the World Online, and contain species that are or have been included within Senecio.<ref name="Senecioneae">Template:Cite journal</ref> Template:Div col

• Aetheolaena Template:Small
• Antillanthus Template:Small
• Barkleyanthus Template:Small
• Bethencourtia Template:Small (synonym Canariothamnus Template:Small)
• Brachyglottis Template:Small<ref name="RecentChanges">Template:Cite journal</ref>
• Curio Template:Small
• Dauresia Template:Small
• Dendrophorbium Template:Small
• Dendrosenecio Template:Small - Giant groundsels native to high-elevation areas of East Africa
• Dorobaea Template:Small
• Dresslerothamnus Template:Small
• Elekmania Template:Small
• Hasteola Template:Small
• Herreranthus Template:Small
• Hubertia Template:Small
• Iocenes Template:Small
• Jacobaea Template:Small
• Leonis Template:Small
• Ligularia Template:Small
• Lundinia Template:Small
• Mesogramma Template:Small
• Monticalia Template:Small
• Nelsonianthus Template:Small
• Nesampelos Template:Small
• Oldfeltia Template:Small
• Packera Template:Small
• Pentacalia Template:Small
• Pippenalia Template:Small
• Pittocaulon Template:Small
• Pojarkovia Template:Small
• Psacaliopsis Template:Small
• Pseudogynoxys Template:Small
• Robinsonia Template:Small (synonym Vendredia Template:Small)
• Roldana Template:Small
• Sinosenecio Template:Small
• Synotis Template:Small
• Telanthophora Template:Small
• Tephroseris Template:Small
• Zemisia Template:Small<ref name="GRIN">Template:Cite web</ref>

Etymology

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

Selected species

• Senecio ampullaceus Template:Small — Texas ragwort, Texas squaw-weed, Texas groundsel, clasping-leaf groundsel<ref name="kyledaily">Template:Cite web</ref>
• Senecio angulatus Template:Small — creeping groundsel
• Senecio antisanae Template:Small
• Senecio arborescens
• Senecio barbertonicus Template:Small — succulent bush senecio
• Senecio bigelovii Template:Small — nodding groundsel
• Senecio brasiliensis Template:Small — flor-das-almas
• Senecio cambrensis Template:Small — Welsh groundsel, Welsh ragwort
• Senecio candicans Template:Small — angel wings
• Senecio casapaltensis Template:Small (synonym Senecio sanmarcosensis Template:Small)
• Senecio crassissimus Template:Small
• Senecio decaryi Template:Small — Madagascar senecio
• Senecio elegans Template:Small — purple groundsel
• Senecio falklandicus Template:Small
• Senecio flaccidus Template:Small — Douglas senecio, threadleaf groundsel, threadleaf ragwort
• Senecio gallicus Template:Small — French groundsel
• Senecio glaucus Template:Small — Jaffa groundsel
• Senecio howeanus Template:Small
• Senecio inaequidens Template:Small — South African ragwort
• Senecio iscoensis Template:Small
• Senecio keniophytum Template:Small
• Senecio lamarckianus Template:Small
• Senecio leucanthemifolius Template:Small — coastal ragwort
• Senecio macroglossus Template:Small — Natal ivy, wax ivy
• Senecio madagascariensis Template:Small — Madagascar ragwort
• Senecio neowbsteri Template:Small – Olympic Mountain groundsel
• Senecio oxyriifolius Template:Small (synonym Senecio tropaeolifolius) — false nasturtium
• Senecio patagonicus Template:Small
• Senecio pauciradiatus Template:Small
• Senecio pokohinuensis Template:Small — Mokohinau groundsel
• Senecio pulcher Template:Small
• Senecio scandens Template:Small — climbing Senecio
• Senecio squalidus Template:Small — Oxford ragwort
• Senecio triangularis Template:Small — arrowleaf groundsel
• Senecio vaginatus Template:Small
• Senecio vernalis Template:Small — eastern groundsel
• Senecio viscosus Template:Small — sticky ragwort
• Senecio vulgaris Template:Small — 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 Template:Small (as S. grandifolius Template:Small)
• Tephroseris papposa Template:Small (as S. papposus)

Distribution

The genus Senecio is distributed almost worldwide.<ref name="Senecioneae" /> 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.

External links

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• Template:Cite webTemplate:Gutenberg