Senecio


Senecio is a genus of flowering plants in the daisy family 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.

Description

Morphology

The flower heads are often 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.

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.
[Image:Senecio.barbertonicus.7074.jpg|thumb|190px|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.Aetheolaena Antillanthus Barkleyanthus Bethencourtia Brachyglottis Curio Dauresia Dendrophorbium Dendrosenecio - Giant groundsels native to high-elevation areas of East AfricaDorobaea Dresslerothamnus Elekmania Hasteola Herreranthus Hubertia Iocenes Jacobaea Leonis Ligularia Lundinia Mesogramma Monticalia Nelsonianthus Nesampelos Oldfeltia Packera Pentacalia Pippenalia Pittocaulon Pojarkovia Psacaliopsis Pseudogynoxys Robinsonia Roldana Sinosenecio Synotis Telanthophora Tephroseris

Etymology

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

Selected species

Formerly in Senecio Brachyglottis greyi Jacobaea vulgaris

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.