The current interpretation of the widespread Opuntia dillenii (Ker-Gawler) Haworth is controversial. In Hunt et al. (2006, text: 201), the taxon is considered to be synonymous with the equally widespread Opuntia stricta (Haworth) Haworth, and defined as "the widespread spiny form of O. stricta" (ibidem). It is interesting to note that the three photos representing O. stricta in NCL (ibidem, atlas: 499, 499.4, 499.5, 499.6), always show only the dillenii form, with an obovate segment, never the stricta form. Anderson (2001, 495, 520-521) and Anderson & Eggli (2011, 455-456, 478), keep the two taxa separate, the latter showing for O. stricta a taxon with an elliptical segment (2011, 478). Both Anderson (2001, 495) and Anderson & Eggli (2011, 456) report that in the past Benson (1982, 500) believed that the two taxa were the same species, while Howard & Touw (1982) have kept the two species separate. As far as we are concerned, we found Benson's documentation convincing (1982, 497-501), which considers O. dillenii to be a variety of O. stricta, showing that in Florida the populations of the two taxa overlap in many areas, in which only on a few occasions the two forms (i.e. O. stricta with a more or less elliptical segment, spineless and O. dillenii with an obovate segment and 1-11 spines for areola) are distinguishable from each other. The author shows an accurate photographic documentation of the two forms, and of the transitions between them. Benson also adds that in the Caribbean islands the dillenii form completely replaces the stricta form. Having  documented the transition between the two forms in the southern United States, we consider O. dillenii a part of the same dominant biological unit bearing the name O. stricta. Below is the distribution of the taxon thus conceived: Bahamas; Bonaire, Sint Eustatius and Saba (Bonaire, Sint Eustatius, Saba); Brazil (Alagoas, Bahia, Paraíba, Pernambuco, Sergipe); Cayman Islands; Cuba; Curaçao; Dominican Republic; Ecuador; Jamaica; Mexico (Campeche, Oaxaca, Querétaro, Quintana Roo, San Luis Potosí, Tabasco, Tamaulipas, Veracruz, Yucatán); Puerto Rico; Sint Maarten (Dutch part); Saint Martin (French part); United States (Alabama, Florida, Georgia, South Carolina, Texas); Venezuela; Virgin Islands (data gathered from: Durán, R., Gómez-Hinostrosa, C., Hernández, H. M., Tapia, J. L., Terrazas, T. & Loaiza, C. 2017. Opuntia stricta (amended version of 2013 assessment). The IUCN Red List of Threatened Species 2017. Downloaded on 24 January 2020. Note: Puerto Rico, is taken from the distribution of O. dillenii  in  Anderson (2001, 495) and in Anderson & Eggli (2011, 455). (Quoted from Anceschi & Magli 2021, 76-77)