A new species and three new varieties of the genus Senecio L. sect. Senecio, are described. The new species, S. pichineuquensis Tortosa and Adr. Bartoli, included in the series Xerosenecio (Cabrera) Cabrera and S. E. Freire, has a geographic distribution in the south of Mendoza and north of Neuquén Provinces. It is characterized by ligneous rigid stems with long internodes, linear, rigid leaves, few-flowered discoid yellow heads grouped in dense corymbs, and narrowly cylindrical involucre. A key is provided for its differentiation from the allied species. A variety of this species with cream-color heads, S. pichineuquensis var. albus Tortosa and Adr. Bartoli, is described. The other two new varieties, S. bracteolatus Hook. et Arn. var. luteous Tortosa and Adr. Bartoli and S. varvarcensis Cabrera var. pinnatus Tortosa and Adr. Bartoli, belong also to the series Xerosenecio, and are apparently endemic to the north of Neuquén Province. The variety luteous of S. bracteolatus differs from the typical variety by its gold yellow florets, higher narrowly cylindrical involucre, and lower number of phyllaries and flowers, whereas the variety pinnatus of S. varvarcensis may be distinguished from the typical variety by its pinnate leaves (vs. entire leaves in var. varvarcensis). Two other species of Senecio that inhabit in Patagonia are included in the synonymy of different species: S. subdiscoideus Sch. Bip. ex Wedd. of the series Metazanthi (Meyen) Cabrera et S. E. Freire, as synonym of S. kingii Hook. f., and S. bipontinii Wedd. of the series Chilenses DC. ex M. G. López, A. F. Wulff and Xifreda subseries Caespitosi (O. Hoffm.) Cabrera et S. E. Freire as synonym of S. crithmoides Hook. et Arn. S. crithmoides, S. iberidifolius Phil., and S. purpuratus Phil. are lectotipified.
Tortosa, R. D., & Bartoli, A. (2014). Novedades y notas taxonómicas en especies de Senecio de la Patagonia, Argentina. Boletín de la Sociedad Argentina de Botánica,49, (3),p.405-415
Tortosa, Roberto Daniel, Bartoli, Adriana. 2014. "Novedades y notas taxonómicas en especies de Senecio de la Patagonia, Argentina". Boletín de la Sociedad Argentina de Botánica 49, no.3:405-415.
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