''Senecio cadiscus'' is a species of aquatic

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of ...

in the aster family,

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae ...

. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

to the

Western Cape The Western Cape is a province of South Africa, situated on the south-western coast of the country. It is the fourth largest of the nine provinces with an area of , and the third most populous, with an estimated 7 million inhabitants in 2020 ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring count ...

, where it grows in vernal pools. It was at one time classified as ''Cadiscus aquaticus'', the only species in the

monotypic genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

''Cadiscus'', but

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

analysis showed that it is nested within ''

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 Morp ...

''. It is a floating or emergent plant with small narrow leaves and white-rayed flowers. Its populations are small and fragmented, and are declining. The plant is threatened by grazing and trampling by livestock, invasive plants, reclamation of wetlands and

eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...

from fertilizer runoff. The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natur ...

has consequently rated it as " critically endangered".

Taxonomy

This plant was known as ''Cadiscus aquaticus'', the only species in the

''Cadiscus'', until

analyses indicated it was clearly nested among the species of ''

''. It was moved there and renamed ''S. cadiscus'' in 2009. Some authorities still accept its former name.

Description

This is an

aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments ( saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

that grows in

vernal pool Vernal pools, also called vernal ponds or ephemeral pools, are seasonal pools of water that provide habitat for distinctive plants and animals. They are considered to be a distinctive type of wetland usually devoid of fish, and thus allow the safe ...

s. It is floating or emergent and sometimes terrestrial along the pool margins. Young plants are submerged. Flowering occurs in August and September. The plant has narrow, floating leaves and white ray florets. The fruit is a cypsela with a pappus of coarse bristles and small tufts of hairs that become sticky and slimy when wet. These may be adaptations to zoochory, in which seeds are dispersed by animals, perhaps

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which i ...

. Nordenstam, B., et al. (2009)
The South African aquatic genus ''Cadiscus'' (Compositae-Senecioneae) sunk in ''Senecio''.
''Compositae Newsletter'' 47: 28–32.

Status

The plant is restricted to vernal pool habitat. It is known from a few localities, and has been recently

extirpated Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...

from a few others. It does not occur in all of the vernal pools that are apparently available to it, and it probably does not have the ability to

disperse Disperse was a Christian rock band from Southern Indiana active from 1996 to 2004. The band was formerly known, with an adjusted roster, as "Stuff." Members (as of 2004 dispersion) :Chelsey Pieratt - Vocals :Chris Billings - Lead Guitar :Andy ...

easily. Populations are thought to have declined over 70% in the last 100 years, and declines are ongoing. Threats to the plant and its vernal pool ecosystem include

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and other ...

and trampling by

cattle Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Adult females are referred to as cows and adult ...

and

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million ...

s, reclamation of

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...

s, use of heavy machinery on the land,

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...

grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in law ...

es introduced when livestock feed is discarded in the area, and

from

fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

runoff.''Senecio cadiscus''.
Red List of South African Plants. South African National Biodiversity Institute (SANBI).

References

{{Taxonbar, from1=Q5016507, from2=Q15552160, from3=Q65929922 cadiscus Endemic flora of the Cape Provinces Taxobox binomials not recognized by IUCN