Simsia

Simsia is a genus of flowering plants in the tribe Heliantheae within the family Asteraceae.[3][6] It includes annuals, herbaceous perennials, and shrubs. They range from the western United States south through Central and South America to Argentina, with the center of diversity occurring in Mexico. The genus is named for British physician and botanist John Sims (1749–1831).[7] 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 and other Asteraceae. Some species are known by the common name bushsunflower.[8]

For the earthworm genus, see Simsia (annelid).

Simsia
Simsia calva
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Subfamily: Asteroideae
Tribe: Heliantheae
Subtribe: Helianthinae
Genus: Simsia
Pers. 1807,[1] not R. Br. 1810 (Proteaceae)[2]
Type species
Simsia amplexicaulis[3][4]
Synonyms[5]
  • Encelia sect. Simsia (Pers.) A.Gray
  • Barrattia A.Gray & Engelm. ex A.Gray

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). There are, however, several species in which the cypsela is biconvex, 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.[7]

The genus was thoroughly studied by Spooner[9] using comparative morphology, chromosome counts, and crossing experiments, and based on samples from wide-ranging field work. Subsequently two new species have been documented,[10] 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, it is now firmly established that Simsia is part of subtribe Helianthinae (the taxonomic group which includes the common sunflower, Helianthus annuus), and is a close relative of Tithonia[7][11]

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.[4]

Species[5][12][13]
Formerly included[5]

numerous species now regarded as members of other genera: Encelia Geraea Iostephane Viguiera

References
  1. "Genus: Simsia Pers". Germplasm Resources Information Network. United States Department of Agriculture. 1996-09-17. Retrieved 2011-02-13.
  2. Tropicos, Simsia R. Br.
  3. Tropicos, Simsia Pers.
  4. Robinson, Harold Ernest; Brettell, R. D. (1972). "Studies in the Heliantheae (Asteraceae). II. A survey of the Mexican and Central American species of Simsia". Phytologia. 24 (5): 361–377. doi:10.5962/bhl.part.17146.
  5. Flann, C (ed) 2009+ Global Compositae Checklist Archived 2014-11-06 at archive.today
  6. Persoon, Christiaan Hendrik. 1807. Synopsis Plantarum 2: 478-479 in Latin
  7. Spooner, David M. "Simsia Persoon, Syn. Pl. 2: 478. 1807". Flora of North America. eFloras.org. Retrieved 2011-12-30.
  8. USDA, NRCS (n.d.). "Simsia". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 15 November 2015.
  9. Spooner, D. M. 1990. Systematics of Simsia (Compositae-Heliantheae). Systematic Botany Monographs 30: 1-90.
  10. Panero, J. L.; E. E. Schilling (1992). "Two new species of Simsia from southern Mexico". Novon. 2 (4): 35–38. doi:10.2307/3391498. JSTOR 3391498.
  11. Schilling, E. E.; J. L. Panero (1996). "Phylogenetic reticulation in subtribe Helianthinae". American Journal of Botany. 83 (7): 939–948. doi:10.2307/2446272. JSTOR 2446272.
  12. The Plant List search for Simsia
  13. Biota of North America Program 2013 county distribution maps
  14. "Simsia". Integrated Taxonomic Information System. Retrieved 2011-02-13.
  15. "GRIN Species Records of Simsia". Germplasm Resources Information Network. United States Department of Agriculture. Retrieved 2011-02-13.
  • Media related to Simsia at Wikimedia Commons
  • Data related to Simsia at Wikispecies
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