Acanthospermum Schrank
Acanthospermum is a small genus of six or eight species, all originally native to South and Central America. It is closely related to Melampodium, morphologically as well as genetically (e.g. Stuessy 1970, Blöch & al. 2009). Several species are noxious agricultural weeds and now have a pantropical distribution. One of these, Acanthospermum hispidum, has been recorded as an alien in Belgium.
Literature:
Blake S.F. (1921) Revision of the genus Acanthospermum. Contr. U.S. Natl. Herb. 20: 383-392. [available online at: https://archive.org/details/cbarchive_119975_revisionofthegenusacanthosperm9999]
Blöch C., Weiss-Schneeweiss H., Schneeweiss G.M., Barfuss M.H., Rebernig C.A., Villasenor J.L. & Stuessy T.F. (2009) Molecular phylogenetic analyses of nuclear and plastid DNA sequences support dysploid and polyploid chromosome number changes and reticulate evolution in the diversification of Melampodium (Millerieae, Asteraceae). Mol. Phylogenet. Evol. 53: 220-233. [available online at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4268500/]
Pruski J.F. 1997 (1324) Proposal to conserve the name Acanthospermum against Centrospermum (Compositae, Heliantheae). Taxon 46(4): 805-806.
Strother J.L. (2006) Acanthospermum. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 21. Oxford University Press, New York-Oxford: 33-36. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=100132]
Stuessy T.F. (1970) The genus Acanthospermum (Compositae-Heliantheae-Melampodinae): taxonomic changes and generic affinities. Rhodora 72: 106-109. [available online at: http://biostor.org/reference/138152]
Stuessy T.F. (1971) Chromosome numbers and phylogeny in Melampodium (Compositae). Amer. J. Bot. 58(8): 723-736.