''Simsia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

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 ...

s in the tribe

Heliantheae The Heliantheae (sometimes called the sunflower tribe) are the third-largest tribe in the sunflower family (Asteraceae). With some 190 genera and nearly 2500 recognized species, only the tribes Senecioneae and Astereae are larger. The name is d ...

within the 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 ...

.Tropicos, ''Simsia'' Pers.
/ref> It includes annuals,

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition ...

perennials A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

, and shrubs. They range from the

western United States The Western United States (also called the American West, the Far West, and the West) is the region comprising the westernmost states of the United States. As American settlement in the U.S. expanded westward, the meaning of the term ''the Wes ...

south through

Central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known a ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

, with the center of diversity occurring in Mexico. The genus is named for British physician and botanist John Sims (1749–1831). Although some species are relatively rare, others have become common weeds that line the roadsides and fields of Mexico, often forming dense stands mixed with ''

Tithonia ''Tithonia'' is a genus of flowering plants in the tribe Heliantheae within the family Asteraceae. ''Tithonia'' has a center of distribution in Mexico but with one species extending into the Southwestern United States and several native to Centr ...

'' and other

. Some species are known by the common name bushsunflower.

Description and systematics

A feature that characterizes many of the species of the genus and helps to distinguish them from related genera is the extremely flattened cypsela (

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not op ...

). There are, however, several species in which the cypsela is

biconvex Biconvex may refer to: * Biconvex bipartite graph * Biconvex lens * Biconvex optimization Biconvex optimization is a generalization of convex optimization Convex optimization is a subfield of mathematical optimization that studies the problem ...

, and these are recognized as belonging to ''Simsia'' by a group of other, mostly technical features, including nodal disks (stipule-like appendages at the base of the petioles), relatively long and narrow ray ovaries, and long and tapering style branches that lack a pronounced apical appendage. The genus was thoroughly studied by Spooner using comparative morphology, chromosome counts, and crossing experiments, and based on samples from wide-ranging field work. Subsequently two new species have been documented, and additional species are being transferred into the genus. Although at one time, ''Simsia'' was considered to be related to other genera with flattened cypselae, such as ''

Encelia ''Encelia'' is a genus of the plant family Asteraceae. It consists of shrubs (and one geophyte) of arid environments in southwestern North America and western South America. All have n = 18 chromosomes. All the North American species are ob ...

'', it is now firmly established that ''Simsia'' is part of subtribe Helianthinae (the taxonomic group which includes the common sunflower, ''

Helianthus annuus The common sunflower (''Helianthus annuus'') is a large annual forb of the genus ''Helianthus'' grown as a crop for its Sunflower seed, edible oily seeds. Apart from sunflower oil, cooking oil production, it is also used as livestock forage (as ...

''), and is a close relative of ''Tithonia'' All of the species for which chromosome counts have been made are diploid (''x'' = 17), and crossing experiments suggest that there are few barriers to hybridization between species of the genus. Natural hybridization appears to occur and may complicate identification of some specimens, particularly involving the weedy species such as ''S. foetida'', ''S. amplexicaulis'', and ''S. lagascaeformis''. ; SpeciesFlann, C (ed) 2009+ Global Compositae Checklist
Biota of North America Program 2013 county distribution maps
/ref> * ''

Simsia amplexicaulis ''Simsia amplexicaulis'' is a species of flowering plant in the 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. C ...

'' (Cav.) Pers. - Guatemala, Honduras, Mexico (from

Chihuahua Chihuahua may refer to: Places *Chihuahua (state), a Mexican state **Chihuahua (dog), a breed of dog named after the state **Chihuahua cheese, a type of cheese originating in the state **Chihuahua City, the capital city of the state **Chihuahua Mun ...

Chiapas Chiapas (; Tzotzil and Tzeltal: ''Chyapas'' ), officially the Free and Sovereign State of Chiapas ( es, Estado Libre y Soberano de Chiapas), is one of the states that make up the 32 federal entities of Mexico. It comprises 124 municipalities ...

) * ''Simsia annectens'' S.F.Blake -

, Michoacán, Oaxaca, Guerrero, México State, Jalisco, Nayarit * ''Simsia calva'' (A.Gray) A.Gray – Awnless bush sunflower - Nuevo León, Coahuila, Hidalgo (state), Hidalgo, Tamaulipas, United States (Texas, TX New Mexico, NM) * ''Simsia caucana'' Cuatrec. - Cauca Department, Cauca in Colombia * ''Simsia chaseae'' (Millspaugh) S.F.Blake - Veracruz, Yucatán Peninsula * ''Simsia dombeyana'' (A.Gray) S.F.Blake - Venezuela, Ecuador, Peru, Brazil, Bolivia, Paraguay,

* ''Simsia eurylepis'' S.F.Blake - San Luis Potosí, Tamaulipas, Veracruz, Campeche, Nuevo León * ''Simsia foetida'' (Cav.) S.F.Blake - from Michoacán to Nicaragua * ''Simsia fruticulosa'' (Sprengel) S.F.Blake - Colombia, Venezuela, Ecuador * ''Simsia ghiesbreghtii'' (A.Gray) S.F.Blake -

, Guatemala * ''Simsia grandiflora'' Benth. ex Oerst. - Nicaragua, Honduras, El Salvador, Guatemala,

* ''Simsia guatemalensis'' H.Rob. & Brettell - Honduras, El Salvador, Guatemala * ''Simsia hispida'' (Kunth) Cass. - San Luis Potosí, Michoacán, México State * ''Simsia holwayi'' S.F.Blake - Guatemala,

* ''Simsia jamaicensis'' S.F.Blake - Jamaica * ''Simsia lagasceiformis'' DC. – Annual bush sunflower - Mexico, Guatemala, United States (Arizona, AZ Texas, TX New Mexico, NM) * ''Simsia molinae'' H.Rob. & Brettell - Honduras, Nicaragua * ''Simsia pastoensis'' Triana - Colombia * ''Simsia sanguinea'' A.Gray - El Salvador, Guatemala,

, Oaxaca, Puebla, Veracruz, Michoacán, Morelos, México State, Jalisco * ''Simsia santarosensis'' Spooner - Costa Rica * ''Simsia setosa'' S.F.Blake - Sonora, Durango, Nayarit * ''Simsia steyermarkii'' H.Rob. & Brettell - Guatemala * ''Simsia subaristata'' A.Gray - Nuevo León * ''Simsia tenuis'' (Fernald) S.F.Blake - Guerrero * ''Simsia villasenorii'' Spooner -

, Oaxaca ; Formerly included numerous species now regarded as members of other genera: ''

Geraea Iostephane Viguiera''

References

* * {{Taxonbar, from=Q4419875 Asteraceae genera Heliantheae