Rebutia Arenacea

''Rebutia'' is a genus of flowering plants in the family Cactaceae, native to Bolivia and Argentina. The limits of the genus have varied widely, depending on whether genera such as ''Aylostera'' and ''Weingartia'' are included or treated separately. , Plants of the World Online accepted only three species of ''Rebutia''. A very large number of plants that have been treated in cultivation as species of ''Rebutia'' are now generally regarded as varieties, forms or synonyms of a much smaller number of species, or have been transferred to other genera. Plants treated as ''Rebutia'' are generally small, colorful cacti, globular in form, which freely produce flowers that are relatively large in relation to the body. They have no distinctive ribs, but do have regularly arranged small tubercles. They are considered fairly easy to grow and they may produce large quantities of seeds that germinate freely around the parent plant.

Taxonomy

The genus was designated in 1895 by Karl Moritz Schumann and named after Pierre Rebut (1828–1902), a French cactus nurseryman. The type species is ''R. minuscula'', which has been in cultivation since 1887.

Historical limits of the genus

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'':

(The generic names ''Bridgesia'', ''Spegazzinia'', ''Echinorebutia'', ''Eurebutia'', ''Mediorebutia'', ''Neogymnantha'' and ''Setirebutia'' are invalid, the first two because they are homonyms of ''Bridgesia'' Bert. ex Cambess. and ''Spegazzinia'' Backeb. respectively, the remainder for lack of any valid publication. Some of these are nevertheless valid names for subdivisions of the genus.)

The history of the taxonomic treatment of the genera ''Rebutia'', ''Aylostera'', ''Weingartia'', ''Sulcorebutia'' and ''Cintia'' is summarized below.

The variation in the treatment of the genus is illustrated by the difference between Anderson in 2001, who synonymized genera including ''Aylostera'' and ''Weingartia'' with ''Rebutia'', thereby creating a genus with as many as 41 species, and Mosti et al., who in 2011 separated ''Aylostera'' and ''Weingartia'' (including ''Cintia'' and ''Sulcorebutia'') from ''Rebutia''. , Plants of the World Online agreed with Mosti et al. in keeping ''Aylostera'' separate, and also merged ''Cintia'' and ''Sulcorebutia'' into ''Weingartia'', resulting in ''Rebutia'' having only three species.

Phylogeny

Molecular phylogenetic studies showed that when broadly circumscribed, the genus ''Rebutia'' was polyphyletic. ''Sulcorebutia'' and ''Weingartia'' were kept as separate genera in a 2007 study whose summary cladogram for those species studied is shown below.. Summary cladogram based on Fig. 2.

Species formerly classified as ''Weingartia'', ''Sulcorebutia'' and ''Cintia'' showed a close relationship to each other and to species of ''Rebutia'' with naked pericarpels (''Rebutia'' II above), including the type species ''R. minuscula''. The larger group of species of ''Rebutia'' studied, those with hairy or bristly pericarpels, formed a separate, more distantly related clade (''Rebutia'' I). It was suggested that these be excluded from the genus, and , Plants of the World Online placed them in the genus ''Aylostera''.

Species

The number of species has been debated, because of disagreement both over what constitutes the genus and what constitutes a species. A very large number of plants that have circulated as species of ''Rebutia'' are now generally regarded as varieties, forms or synonyms of others. E. F. Anderson recognised 41 species in 2001.Edward F. Anderson, ''The Cactus Family'', Portland, Oregon: Timber Press, 2001, pp.599-611. Only the following three species were accepted by Plants of the World Online .

Gallery

File:Rebutia minuscula4.jpg, ''Rebutia minuscula'' – first discovered ''Rebutia''
File:Rebutia grandiflora 1.jpg, ''Rebutia minuscula'' f. ''grandiflora'' – form with largest flower
File:Rebutia kariusiana 1.jpg, ''Rebutia minuscula'' var. ''minuscula'' (syn. ''Rebutia kariusiana'')
File:Rebutia krainziana 2.jpg, ''Rebutia minuscula'' var. ''minuscula'' (syn. ''R. krainziana'')
File:Rebutia marsoneri pm.JPG, ''Rebutia minuscula'' var. ''minuscula'' (syn. ''Rebutia marsoneri'')
File:Rebutia_senilis_1.jpg, ''Rebutia minuscula'' var. ''minuscula'' (syn. ''R. senilis'') – form with orange red flowers
File:Rebutia senilis lilacino-rosea 1.jpg, ''Rebutia minuscula'' var. ''minuscula'' (syn. ''R. senilis'') – form with rose flower
File:Rebutia chrysacantha kesselringiana 1.jpg, ''Rebutia minuscula'' var. ''minuscula'' (syn. ''R. chrysacantha'') – form with yellow flower
File:Rebutia violaciflora 1.jpg, ''Rebutia minuscula'' var. ''minuscula'' (syn. ''R. violaciflora'') – form with violet flower
File:Rebutia padcayensis.jpg, ''Rebutia padcayensis'' (syn. ''R. margarethae'')

Notes and references

External links

*
''Rebutia'' — Names and Identification

Cactiguide.com: ''Rebutia''

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Cacti of South America
Flora of Argentina
Flora of Bolivia
Cereeae genera