Rebutia formerly included a large number of species, including the plants now included in the genera Aylostera & Weingartia. In recent years studies of DNA have shown that these genera were derived from different evolutionary lines. Superficially Rebutia resemble Aylostera in appearance, but in fact are more closely related to Weingartia than they are to Aylostera.
Differences between Rebutia and Aylostera include that in Rebutia the flowers tend to be uniformly coloured and have no hairs or bristles, whereas in Aylostera flowers are often bicoloured or multi-toned, have contrasting stamens and/or styles, and have hairs or bristles.
The distribution area for Rebutia is mainly northern Argentina, extending a little into Bolivia.
The genus Rebutia currently comprises twelve species according to Mosti et al. (2011):