20. Sida spinosa Linnaeus (1753: 683–684) (Figures 10, 11E–K, 14S)

Holotype:—“ Habitat in India ” (LINN 866.1! [digital image]).

Taxonomic notes: — Sida spinosa belongs to section Spinosae (Fryxell 1985) (Table 1). One of its striking features is the presence of a small projection, tubercle, such as a spine, but not sharp, in the base of petioles. This feature can also be found in Sida riedelii, a very similar species, that is distinguished by the hyaline and crumbly dorsal face of its mericarps (Schumann 1891, Krapovickas 2005), vs. mericarps with complete and reticulated dorsal face, which does not easily break (Figures 11E–K, 14S). The species Sida tuberculata can also present a tubercle at the base of the petioles, which are generally smaller. However, Sida tuberculata, has more than five mericarps.

Distribution, habitat and conservation status: —This species is pantropical, and also occurs in adjacent temperate zones (Fryxell 1985, Fuertes Aguilar 1995, Brandão et al. 2017). In Brazil S. spinosa occurs in northeast, southeast, midwest and south (Bovini 2020) and in all regions of Rio Grande do Sul state (Figure 10), in ruderal environments and anthropized grasslands, except in Coastal grassland. The species is here considered Least Concern (LC) because it has large EOO and AOO, since it is a frequent and ruderal species, widely distributed.

Representative specimens: — BRAZIL. Rio Grande do Sul. Augusto Pestana, Rosário, 19 February 1954, J . Pivetta 879 (ICN, PACA); Barra do Quaraí, Parque Estadual do Espinilho, 30º11’22.5” S 57º29’46.5” W, 16 December 2019, M. Grings & R. Paniz 908 (ICN); Boa Vista do Incra, Projeto de Assentamento 28 de abril, 03 April 2009 , M. Grings 2060 (ICN); Caçapava do Sul, próximo a Pedra do Segredo, 23 November 2018 , M. Grings & J. Schaefer 1971 (ICN); Derrubadas, Parque Estadual do Turvo, December 1982 , D. B. Falkenberg 302 (FLOR); Gravataí, Cachoeirinha, 07 January 1949 , B. Rambo s.n. (PACA 39567); Uruguaiana, BR- 290, 154 m, WGS 84 S -29.86468º W -056.88529º, 03 December 2020, M. Grings et al. 2198 (ICN).