Gamochaeta Wedd.
Gamochaeta is a segregate of Gnaphalium and obviously closely related to it. Its generic status is controversial. Many recent authors, especially in the New World (e.g. Freire & Iharlegui 1997, Nesom 2006), acknowledge its generic status, while others are more reluctant to do so (e.g. Stace 2010, Tison & de Foucault 2014). However, molecular data seem to favor its segregation from Gnaphalium (e.g. Schilling & Floden 2012, Freire & al. 2014). It is best distinguished by pappus bristles that are basally connate (entire pappus falling as a unit). In Gnaphalium pappus bristles are distinct and fall separately. As currently circumscribed Gamochaeta probably accommodates ca. 50-80 species, depending on species circumscription. All are native to the New World, with its center of diversity being located in South America. Several species are reputed environmental weeds and have widely spread beyond their native distribution range (e.g. Drury 1971, Rocha Afonso 1984). In addition to the single species treated in detail below, the following are in expansion in southwestern France (especially in coastal areas) and probably will reach Belgium in the future: Gamochaeta antillana and G. coarctata (Willd.) Kerguélen (syn.: G. spicata Cabrera, Gnaphalium coarctatum Willd., G. spicatum Lam.). The former, despite being a relatively recent introduction (Vivant 1980), at present (2014) reaches Nantes in western France (see: http://www.tela-botanica.org/bdtfx-nn-101209-synthese).
Additional aliens: Gamochaeta antillana (Urban) Anderberg (syn.: G. subfalcata (Cabrera) Cabrera, Gnaphalium antillanum Urban and G. subfalcatum Cabrera) (Am., wool alien). An old collection of G. calviceps (Fernald) Cabrera (syn.: Gnaphalium calviceps Fernald) (Verloove 2006) eventually turned out to be referable to G. antillana (comm. G. Nesom).
Literature:
Alford M.H. (2012) New records of Gamochaeta (Asteraceae) in the Hawaiian Archipelago. Bishop Museum Occasional Papers 113: 1-6. [available online at: http://hbs.bishopmuseum.org/pubs-online/pdf/op113p1-6.pdf]
Anderberg A.A. (1991) Taxonomy and phylogeny of the tribe Gnaphalieae. (Asteraceae) Opera Botanica 104: 1-195.
Cabrera A.L. (1961) Observaciones sobre las Inuleae-Gnaphalineae (Compositae) de America del Sur. Bol. Soc. Argent. Bot. 9: 359-386.
Dillon M.O. & Sagstegui-Alva A. (1991). Sinopsis de los generos de Gnaphaliinae (Asteraceae-Inuleae) de Sudamerica. Arnaldoa 1(2): 5-91. [available online at: http://biostor.org/reference/139965]
Drury D.G. (1971) The American spicate cudweeds adventive to New Zealand (Gnaphalium Section Gamochaeta-Compositae). New Zealand J. Bot. 9(1): 157-185. [available online at: http://www.tandfonline.com/doi/pdf/10.1080/0028825X.1971.10430174]
Freire S.E., Chemisquy M.A., Anderberg A.A., Beck S.G., Meneses R.I., Loeuille B. & Urtubey E. (2014) The Lucilia group (Asteraceae, Gnaphalieae): phylogenetic and taxonomic considerations based on molecular and morphological evidence. Pl. Syst. Evol. (doi:10.1007/s00606-014-1147-0).
Freire S.E. & Iharlegui L. (1997) Sinopsis preliminar del género Gamochaeta (Asteraceae, Gnaphalieae). Bol. Soc. Argent. Bot. 33: 23-35.
Hilliard O.M. & Burtt B.L. (1981) Some generic concepts in Compositae – Gnaphaliinae. J. Linn. Soc. Bot. 82: 181-232.
Nesom G.L. (1990) The taxonomic status of Gamochaeta (Asteraceae: Inuleae) and the species of the United States. Phytologia 68: 186-198. [available online at: http://biostor.org/reference/62827]
Nesom G.L. (2004) New species of Gamochaeta (Asteraceae: Gnaphalieae) from the eastern United States and comments on similar species. Sida, Contrib. Bot. 21(2): 717-741.
Nesom G.L. (2004) New distribution records for Gamochaeta (Asteraceae: Gnaphalieae) in the United States. Sida, Contrib. Bot. 21(2): 1175-1185. [available online at: http://www.guynesom.com/Gamochaetarecords.pdf]
Nesom G.L. (2006) Gamochaeta. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 19. Oxford University Press, New York-Oxford: 431-438. [available online at: http://efloras.org/florataxon.aspx?flora_id=1&taxon_id=113220]
Nesom G.L. (2007) Distribution of Gamochaeta (Asteraceae: Gnaphalieae) in Texas, Oklahoma, Arkansas, and Louisiana. Journal of the Botanical Research Institute of Texas 1(2): 1125-1130.
Rocha Afonso M.L. (1984) Contribuição para o conhecimento do género Gamochaeta Weddell em Portugal continental e insular. Bol. Soc. Brot., sér. 2 57: 113-127.
Schilling E.E. & Floden A. (2012). Barcoding the Asteraceae of Tennessee, tribes Gnaphalieae and Inuleae. Phytoneuron 2012-99: 1-6. [available online at: http://www.phytoneuron.net/99PhytoN-TennGnaphalieae.pdf]
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Tison J.-M. & de Foucault B. (coord.) 2014) Flora Gallica. Flore de France. Editions Biotope, Mèze : xx + 1196 p.
Verloove F. (2006) Catalogue of neophytes in Belgium (1800-2005). Scripta Botanica Belgica 39: 89 p.
Vivant J. (1980) Phanérogames adventices se naturalisant dans les Landes et les Pyrénées-Atlantiques. Bull. Soc. Bot. Fr., Lettres Bot. 127(3): 289-295. [available online at: http://www.tandfonline.com/doi/pdf/10.1080/01811797.1980.10824456]