There has been considerable debate about the extent of the genus. In the middle of the twentieth century there was a tendency to separate groups of plants within "Rebutia" as new genera, e.g. "Mediolobivia", whereas towards the end of the century the reverse tendency predominated, with genera previously regarded as separate, such as "Weingartia", being subsumed within "Rebutia". At the beginning of the twenty-first century there was a broad consensus, as reflected in Kew's list of Vascular Plant Families and Genera, that the following genera should be regarded as synonyms of "Rebutia":