Amberboa Vaill.
Amberboa is a genus related to Centaurea and it has often been included in it. It differs by cypselae with a denticulate apex and a conspicuous rim around the basal scar. It also differs cytologically (with a higher chromosome base number than that in most species of Centaurea s.str.; Keil 2006). Molecular phylogenetic studies confirms it generic status (e.g. Susanna & al. 1995). As currently circumscribed Amberboa counts ten or more species, ranging from the eastern Mediterranean area to Central Asia. It is probably most diverse in Iran where more than half of the species occur (e.g. Ranjbar & Negaresh 2013, Negaresh 2015). A single species, Amberboa moschata, is a more or less widely cultivated ornamental and has been recorded as an escape in Belgium.
Literature:
Gabrielian E.T. (2011) Two new species of Amberboa (Asteraceae, Cardueae) from Central Asia. Takhtajania 1: 35-38. [available online at: http://takhtajania.asj-oa.am/9/1/35-1.pdf]
Gabrielian E. & Jarvis C.E. (1996) Amberboa moschata, A. glauca, and A. amberboi (Asteraceae: Cardueae). A note on their taxonomy and typification of their names. Taxon 45: 213-215.
Iljin M.M. (1932) A critical survey of the genus Amberboa Less. Izv. Bot. Sada Akad. Nauk S.S.S.R. 30: 101-116.
Keil D.J. (2006) Amberboa. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 19. Oxford University Press, New York-Oxford: 172-173. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101284]
Negaresh K. (2015) Amberboa maroofii (Asteraceae, Cardueae–Centaureinae), a new species from Kurdistan, Iran. Phytotaxa 195(2): 171-177.
Ranjbar M. & Negaresh K. (2013) A contribution to the genus Amberboa (Asteraceae, Cardueae, Centaureinae) from Iran. Willdenowia 43: 271-277. [available online at: http://www.bioone.org/doi/pdf/10.3372/wi.43.43206]
Susanna A., Garcia-Jacas N., Soltis D.E. & Soltis P.S. (1995) Phylogenetic relationships in tribe Cardueae (Asteraceae) based on ITS sequences. American Journal of Botany 82: 1056-1068.
Tzvelev N.N. (1998) Amberboa. In: Borisova A.G. (ed.), Flora of the U.S.S.R., vol. 28. Koeltz Scientif Books: 320-330. [available online at: http://www.bioone.org/doi/pdf/10.3372/wi.30.30102]