The genus Sulcorebutia has always been closely linked to the genus Rebutia. The establishement of the genus Sulcorebutia was based on a Rebutia.
Here is a short historical summary.
In 1895, Karl Schumann describes the genus Rebutia as a monotypic genus with Rebutia minuscula as type-species.
In 1922, Britton and Rose, in their “The Cactaceae”, transfer 5 plants from other genera into the genus Rebutia (fiebrigii, steinmannii, deminuta, pseudominuscula and pygmaea).
In 1923, Spegazzini suggests to create a genus Aylostera for plants in which the style is joined, wholly or in part, to the tube. At that time, Rebutia pseudominuscula was the only plant in the case.
In 1931, Dr. Werdermann describes Rebutia steinbachii, that look strange because its body is Lobivia-like but the structure of the flower is Rebutia-like.
Between 1931 and 1951, an incredible number of genus are suggested : Eurebutia, Setirebutia, Chileorebutia, Echinorebutia, Rebulobivia, Neorebutia, Chionorebutia, Dichrorebutia… It must be separated and then it must be combined and then separated again...
In 1951, Curt Backeberg creates the genus Sulcorebutia, monotypic genus with Suclcorebutia steinbachii as type-species. He had noticed a groove in the epidermis at the areole’s tip and thought that the bud was appearing out of that groove.
From 1951 on, Cardenas describes several new species : arenacea, glomeriseta, candiae, menesesii… All described under the genus Rebutia.
In 1964, in his description of Rebutia tunariensis (see Articles), Cardenas doubts about the validity of both genera Aylostera and Sulcorebutia and suggests to recombine them into Rebutia.
In 1972, Brederoo & Donald "complete and improve the diagnose of Backeberg's genus Sulcorebutia" and deplore that Cardenas keeps on describing plants into Rebutia instead of Sulcorebutia. (See Articles)
In the 70's and the 80's a lot of new Sulcorebutia species have been discovered and described by famous collectors such as Ritter, Krahn, Knize, Rausch, Lau, Vasquez, Swoboda...
These days, as a result of a series of studies and DNA analysis conducted by the SSK between 2005 and today (see here), the genera Sulcorebutia, Weingartia and even Cintia seem to be indissociable : "Sulcorebutia and Weingartia should be united into one genus, because neither molecular nor morphological data reveal a distinction between these genera." (Ritz et al., 2007. American Journal of Botany 94(8): p1330.)
On the other hand, they are clearly separated from the genus Rebutia.
Consequentially, Hentzschel & Augustin have published in 2008 in the journal Gymnocalycium 21(2): 767-782 a new classification in an article called : "Weingartia, Sulcorebutia et Cintia - an indivisible unity - new characteristics and new combinations" !
Sulcorebutias are all coming from Bolivia. The brown areas in the map below show more or less the areas where they live. They can be found from an altitude of 1200 m. until 4000 m., most of them growing between 2000 and 3000 m. Such altitudes explain their need for fresh winter temperatures to be able to bloom.
It is interesting to note that the area where the whole lot of Sulcorebutias grow is rather limited : the distance between the most northern point (Cochabamba) and the most southern point (Tarija) is about 500 km. The field of one species is in some cases as large as 2 or 3 soccer pitches ! Can you imagine that such a small area is the only place in the world where grows that species ! Such a small field is of course at the mercy of any trouble. However I don’t think that Sulcorebutias are in danger at
the present time : number of them grow in some hard to reach areas and therefore are rather well protected.
Unfortunately this situation is not a general rule : many cacti are endangered species all over the American continent. Urban development, farming, agriculture, highways, habitat plundering, climate change are some causes of cacti disappearance.
So the least we can do is to take the best care of our plants in our greenhouses and if possible to propagate them. I consider that our collections are a stock for the future !