''Senecio gregorii'', commonly known as annual yellowtop or fleshy groundsel, is a native Australian wildflower species, found in arid and semi-arid regions of the Australia and across the globe. It often grows prolifically after autumn/winter rains, showcasing stunning yellow flowers and fleshy foliage. The scientific name of this species was first published by

Ferdinand von Mueller Baron Sir Ferdinand Jacob Heinrich von Mueller, (german: Müller; 30 June 1825 – 10 October 1896) was a German-Australian physician, geographer, and most notably, a botanist. He was appointed government botanist for the then colony of Vict ...

Description

''Senecio gregorii'' is an erect annual herb that ranges from 15 to 40 centimetres in height. Its stem is simple or branched, with leaves that are broad, linear and up to 9 centimetres long. The leaves can have a succulent appearance, although this varies among the species. It produces clusters of bright yellow flowers that appear from May through to October. Seeds are distributed by wind after the flower sets seed. ''S. gregorii'' reproduces sexually. ''Senecio gregorii'' is distributed predominantly across arid to semi-arid inland Australia. It can tolerate unstable environments and desert-like conditions. It is found growing in a variety of soil types, ranging from white-grey clay to red sand, and has highly versatile habitat types, including clay pans, rocky outcrops and

sand dunes A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, fl ...

Using the

IUCN Red List categories The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biologi ...

, ''S. gregorii'' has been classified as of "

Least Concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

" in Queensland and the Northern Territory. However, it is "

Near Threatened A near-threatened species is a species which has been categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature as that may be vulnerable to endangerment in the near future, but it does not currently qualify fo ...

" in Victoria. The conservation status of ''S. gregorii'' in other states of Australia has not been identified.

Taxonomy

''Senecio gregorii'' is part of the ''Senecio'' genus, which is one of the largest groups of flowering plants, containing over 1,250 species. This genus evolved during the mid to late

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

period. The first publication of the species was documented by

. ''S. gregorii'' was transferred to the genus ''

Othonna ''Othonna'' is a genus of approximately 90 species of succulent or subsucculent perennial herbs or shrubs, with its center of diversity in the Greater Cape Floristic Region (GCFR) of South Africa but some species' ranges include southern Namibia, ...

'' in 1986, but restored to ''Senecio'' in 2004.

Ecology

Native bees (family:

Halictidae Halictidae is the second-largest family of bees (clade Anthophila) with nearly 4,500 species. Halictid species are an extremely diverse group that can vary greatly in appearance. These bees occur all over the world and are found on every contine ...

) are key pollinators of ''S. gregorii'' plants, allowing both species to persist in their habitats. Some foraging vertebrate and invertebrate animal species rely on ''S. gregorii'' as a food source. For example, caterpillars of the moth ''Heliothis punctifera'' consume ''S. gregorii'' flowerheads before completing their development. Hence, the distribution and abundance of certain animal species depends upon the ecological patterns of ''S. gregorii''. However, ''S. gregorii'' contains

pyrrolizidine alkaloids Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. Pyrrolizidine alkaloids are produced by plants as a defense mechanism against insect he ...

, which act as a defence mechanism against herbivores who have not developed a tolerance for the alkaloids. ''S. gregorii'' is also unpalatable for many animals.

Evolutionary relationships

Adaptive radiation In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic int ...

is rapid and common in ''Senecio'' species, such as ''S. gregorii''. The adaptive diversification of this genus has driven its widespread geographical distribution. Different species (such as those listed above) exhibit unique phylogenetic and morphological characteristics (e.g. leaf shape), owing to the convergence and divergence of species from a common ancestor. Besides adaptive radiation, evidence of

local adaptation Local adaptation is a mechanism in evolutionary biology whereby a population of organisms evolves to be more well-suited to its local environment than other members of the same species that live elsewhere. Local adaptation requires that different po ...

polyploidy Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei ( eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contain ...

and hybridisation has been recorded in ''Senecio'' species.

Image gallery

File:Senecio gregorii habitii.jpg, alt=, ''S. gregorii'' plant File:Senecio gregorii flowers.jpg, alt=, ''S. gregorii'' flower File:Senecio gregorii seeds.jpg, alt=, ''S. gregorii'' seeds File:Senecio gregorii habit.jpg, alt=, ''S. gregorii'' plant

References

{{Taxonbar, from1=Q15598483, from2=Q55915088 gregorii Flora of Australia