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Gamochaeta (Asteraceae, Gnaphalieae) consists of about 60 species primarily distributed in tropical and subtropical America. Gamochaeta americana and G. coarctata are closely related species that have been mainly differentiated by its phyllary apices, plant height, width of basal leaves, and involucre height. In order to evaluate whether G. americana and G. coarctata can be differentiated on a morphological basis, we performed a morphometric analysis. A matrix of 24 morphological characters and 99 specimens was analyzed using two multivariate approaches: Cluster Analysis and Principal Coordinate Analysis. Both, the dendrogram and the Principal Coordinate Analysis (PCoA), showed that the two species are not clearly distinguished. No discriminating morphological characters for the two species have been found. In conclusion, all available data support that G. coarctata should be considered a synonym of G. americana. Lectotype is designated for Gnaphalium purpureum var. macrophyllum, and G. americana is described and illustrated.

Gamochaeta americana (Mill.) Weddell (1856: 151). Gnaphalium americanum Miller (1768: without page). Gnaphalium purpureum var. americanum (Mill.) Klatt (1878: 140). Type:��� JAMAICA. 1731, W. Houston s.n . (lectotype: BM-001009488!, designated by Moore (1936: 206); photo: E-00433391!). Gnaphalium coarctatum Willdenow (1803: 1886). Gnaphalium spicatum Lamarck (1788: 757), nom. illeg. Gnaphalium purpureum var. spicatum Klatt (1878: 140). Gamochaeta spicata Cabrera (1961: 380), nom. superfl. Gamochaeta coarctata (Willd.) Kergu��len (1987: 104). Type:���[URUGUAY]. Monte Video, Oct 1767, P. Commerson s.n. (holotype: P-LAM 00309295!). Gnaphalium consanguineum Gaudichaud (1825: 103). Gamochaeta americana var. alpina Weddell (1856: 152). Gnaphalium spicatum var. alpinum (Wedd.) Hieronymus (1900: 31). Type:��� ARGENTINA. Tierra del Fuego. Islas Malvinas (Falklands Islands), s.d., C. Gaudichaud s.n. (lectotype: P-00704625!, designated by Cabrera (1961: 364)). Gnaphalium spicatum var. chonoticum Hooker (1846: 309). Type:��� CHILE. [Prov. Aysen] Chonos Arch., Dec 1834, C. Darwin [Henslow���s 333] (lectotype: K-000500392!, designated by Porter (1986: 56); isolectotype: CGE). Gamochaeta americana subvar. interrupta Weddell (1856: 152). Type not designated. Gnaphalium purpureum var. macrophyllum Greenman (1904: 97). Type:��� COSTA RICA. El Copey, 1800 m, Feb 1898, A. Tonduz 11771 (lectotype: BR-0000005318742!, designated here; isolectotype: GH-0008342 fragment!). Gnaphalium guatemalense Gandoger (1918: 42). Gamochaeta guatemalensis (Gand.) Cabrera (1961: 363). Type:��� GUATEMALA. Dpto. Alta Verapaz, Feb 1907, H. von Tuerckheim II 1634 (holotype: LY; isotypes: MO, NY, SI!). Gamochaeta irazuensis Nesom (1990b: 199���200). Type:��� COSTA RICA. Volc��n Irazu, 10000���11330 ft., 1 Dec 1937, P.H. Allen 702 (holotype: F-0050254 F!). Annual, biennial to perennial herbs, 5���67 cm tall, stem solitary or more often several ascending stems, unbranched, whitish-woolly, with basal rosette of leaves, rarely approximate, persisting at flowering. Leaves widely obovate or obovate-oblanceolate to oblanceolate, rarely linear-oblanceolate, attenuate at base, apex rounded to obtuse, mucronate, margins flat or wavy toward the apex; strongly bicolored, glabrescent or glabrous and green above, and with appressed white tomentum on lower surface; basal leaves 1.2���9(���12) cm �� 3���20(���25) mm; cauline leaves 1���7.5 cm �� 2���14 mm, gradually reduced in size upwards. Capitula many, in clusters in the axils of the upper leaves, arranged in continuous elongated spikes or only interrupted at the base (inflorescence branched in robust plants). Involucre narrowly campanulate, 3���5 �� 2���3 mm. Phyllaries 18���30, 3���4-seriate, lamina light-brown at apex; outer phyllaries 1���3.5 �� 0.5��� 1.8 mm, ovate, apex obtuse or acute to acuminate, lanuginose; inner phyllaries 2.5���4.5 �� 0.3���1 mm, oblong, apex acute to rounded to short acuminate, glabrous. Pistillate florets 35���136, corolla white-yellowish, purplish at apex, filiform, 2���3 mm long. Bisexual florets 2���7, corolla white-yellowish, purplish at apex, tubular, 2.2���3 mm long.Achenes 0.5���0.8 mm long, pilose, with short globose duplex hairs. Pappus bristles 2.5���3 mm long. Distribution and habitat:��� Gamochaeta americana is widely distributed from the United States of America to Tierra del Fuego and Islas Malvinas (Falkland Islands). Adventive in Eurasia, Africa, Australia, and New Zealand, growing on grassland, moist semi-fixed dunes, and fields on the edge of forests, abandoned crop fields and modified soils along roads, from sea level to 4000 m. Notes:��� The protologue of Gnaphalium purpureum var. macrophyllum mentioned: ��� Costa Rica. El Copey, altitude 1800 m, February, 1898, Ad. Tonduz, no. 11,771 (hb. Gr. and hb. Inst. Phys. Geog. Cost. Ri.)���. We located fragments of the type (leaf and spike) accompanied by an illustration at GH (00008342) and one specimen at BR (0000005318742) with the stamp of ���Herb. Instit. physico-geogr. ��� costaricensis���. We have designated BR-0000005318742 as lectotype because it fully agrees with the protologue of the species. Weddell (1856: 152) placed Gnaphalium americanum Mill., G. purpureum L., G. spicatum Lam., and G. coarctatum Willd. into the synonymy of Gamochaeta americana var. vulgaris Weddell (1856: 152). Nesom (2004a) described two new species, Gamochaeta argyrinea Nesom from the U.S.A. and Puerto Rico, and G. chionesthes Nesom from the U.S.A. In that treatment, Nesom excluded G. americana from the U.S.A. and referred the specimens previously identified as G. americana to G. coarctata (e.g. Nesom 1990a). Our revised concept of G. americana may also include G. argyrinea and G. chionesthes, which have bicolored obovate or obovate-oblanceolate to oblanceolate leaves and capitula arranged in elongated spikes. The multivariate analysis of Gamochaeta is one of our ongoing projects, so before synonymizing G. argyrinea and G. chionesthes with G. americana, we await the outcome of that work., Published as part of Freire, Susana E., Grossi, Mariana A., Iharlegui, Laura, Abarca, Camila L., Monti, Claudia & Bay��n, N��stor D., 2021, Taxonomic Identity of Gamochaeta americana and Gamochaeta coarctata (Gnaphalieae, Asteraceae), pp. 273-283 in Phytotaxa 523 (4) on pages 277-280, DOI: 10.11646/phytotaxa.523.4.1, http://zenodo.org/record/5602472, {"references":["Weddell, H. A. (1856) Chloris Andina. Essai d'une flore de la region alpine des Cordilleres de l'Amerique du Sud. In: Castelnau, F. (Ed.) Expedition dans l'Amerique du Sud, vol. 1. [Partie 1 - 6]. P. Bertrand, Paris, 232 pp. https: // doi. org / 10.5962 / bhl. title. 217","Klatt, F. W. (1878) Die Gnaphalien Amerikas. Eine Studie. Linnaea 42 (1): 111 - 144.","Moore, S. L. M. (1936) Family CXXV. Compositae. In: Fawcett, W. & Rendle, A. B. (Eds.) Flora of Jamaica, vol. 7. British Museum, London, pp. 150 - 289.","Willdenow, C. L. (1803) Species plantarum, ed. 4, vol. 3 (3). G. C. Nauk, Berlin, pp. 1477 - 2409.","Lamarck, J. B. (1788) Encyclopedie Methodique, Botanique, vol. 2. Panckoucke, Paris, 774 pp.","Cabrera, A. L. (1961) Observaciones sobre las Inuleae-Gnaphalineae (Compositae) de America del Sur. Boletin de la Sociedad Argentina de Botanica 9: 359 - 386.","Kerguelen, M. (1987) Donnees Taxonomiques, nomenclaturales et chorologiques pour une revision de la Flore de France. Lejeunia 120: 1 - 264.","Gaudichaud, C. (1825) Rapport sur la Flore des Iles Malouines. Annales des Sciences Naturelles 5: 89 - 110.","Hieronymus, G. H. (1900) Aloysinus Sodiro, S. J.: Plantae ecuadorenses. II. Compositae. Botanische Jahrbucher fur Systematik, Pflanzengeshichte und Pflanzengeographie 29: 1 - 85.","Hooker, J. D. (1846) The Botany of the Antarctic Voyage of H. M. Discovery Ships Erebus and Terror in the Years 1839 - 1843, Under the Command of Captain Sir James Clark Ross. Vol. 1: Flora Antarctica. Reeve Brothers, London, pp. 574. https: // doi. org / 10.5962 / bhl. title. 16028","Porter, D. M. (1986) Charles Darwin's Vascular Plant Specimens from the Voyage of HMS Beagle. Botanical Journal of the Linnean Society 93: 1 - 172. https: // doi. org / 10.1111 / j. 1095 - 8339.1986. tb 01019. x","Greenman, J. M. (1904) New and Otherwise Noteworthy Angiosperms from Mexico and Central America. Proceedings of the American Academy of Arts and Sciences 39 (5): 69 - 120. https: // doi. org / 10.2307 / 20021858","Gandoger, M. M. (1918) Sertum plantarum novarum. Pars prima. Bulletin de la Societe Botanique de France 65: 24 - 69. https: // doi. org / 10.1080 / 00378941.1918.10836046","Nesom, G. L. (1990 b) A new combination and new species in Gamochaeta (Asteraceae: Inuleae) from Central America. Phytologia 68 (3): 199 - 201. https: // doi. org / 10.5962 / bhl. part. 16709","Freire, S. E. (1998) Inuleae. Compositae. In: Bocquet, G. F. & Crosby, M. R. (Eds.) Flora del Paraguay, vol. 27. Conservatoire et Jardin botaniques de la Ville de Geneve-Missouri Botanical Garden, Geneve & St Louis, pp. 1 - 100.","Nesom, G. L. (2004 a) New species of Gamochaeta (Asteraceae: Gnaphalieae) from the eastern United States with comments on similar species. Sida 21: 717 - 741.","Nesom, G. L. (1990 a) Taxonomic status of Gamochaeta (Asteraceae: Inuleae) and the species of the United States. 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Twenty four species of Gamochaeta (Gnaphalieae, Asteraceae), G. aliena, G. alpina, G. americana, G. andina, G. axillaris, G. chamissonis, G. depilata, G. deserticola, G. falcata, G. filaginea, G. humilis, G. longipedicellata, G. neuquensis, G. nivalis, G. oligantha, G. procumbens, G. ramosa, G. serpyllifolia, G. simplicicaulis, G. spiciformis, G. stachydifolia, G. subfalcata, G. valparadisea, and G. villarroelii, are formally monographed with morphological descriptions, illustrations, geographic distribution and habitat, distribution maps, phenology, lists of representative specimens examined, and a comprehensive identification key for every species. A new name Gamochaeta ramosa S.E. Freire, N. Bayón & C.M. Baeza for Gnaphalium ramosum Phil. (1864) non Lam. (1779) nec Sch. Bip. (1845), is proposed. The following taxa are newly synonymized: Gamochaeta foliosa with G. spiciformis; G. monticola with G. oligantha; Gnaphalium petraeum with Gamochaeta andina; G. suffruticosa with G. chamissonis; Gnaphalium bellidifolium, Gamochaeta berteroana with G. filaginea; and Gnaphalium agreste with Gamochaeta stachydifolia. Lectotypes are newly designated for Gnaphalium andinum, G. berteroanum, G. suffruticosum, and G. villarroelii. RESUMEN Este trabajo comprende la revisión de 24 especies de Gamochaeta para Chile, G. aliena, G. alpina, G. americana, G. andina, G. axillaris, G. chamissonis, G. depilata, G. deserticola, G. falcata, G. filaginea, G. humilis, G. longipedicellata, G. neuquensis, G. nivalis, G. oligantha, G. procumbens, G. ramosa, G. serpyllifolia, G. simplicicaulis, G. spiciformis, G. stachydifolia, G. subfalcata, G. valparadisea y G. villarroelii. Se incluye una clave para identificarlas y para cada una de las especies se brinda descripción, ilustración, fenología, distribución geográfica y hábitat, mapa de distribución, material adicional examinado y afinidades taxonómicas. Sobre la base del estudio de los materiales tipo, se establecen los siguientes nuevos sinónimos: Gamochaeta foliosa con G. spiciformis; G. monticola con G. oligantha; Gnaphalium petraeum con Gamochaeta andina; G. suffruticosa con G. chamissonis; Gnaphalium bellidifolium, Gamochaeta berteroana con G. filaginea; Gnaphalium agreste con Gamochaeta stachydifolia; y se propone el nuevo nombre Gamochaeta ramosa S.E. Freire, N. Bayón & C.M. Baeza parar Gnaphalium ramosum Phil. (1864) non Lam. (1779) nec Sch. Bip. (1845). Se designan lectotipos para las siguientes especies: Gnaphalium andinum, G. berteroanum, G. suffruticosum y G. villarroelii.