The following tables were created from information in the article "Hybridizing relationships among the Sinningia species", by the late Martin Mines of New York, published in CrossWords, v4, #2, June 1980, pp. 4-19. It was largely based on published material of Dr. Carl Clayberg.
Updates to the crossing chart were published in later issues of CrossWords, but I have not incorporated them into these tables. My real interest here is to show how many crosses had already been done by 1980. Actually, most of them were the work of Clayberg in the mid-1960s. I had a hard time getting S. leucotricha x douglasii to bloom, but it was already known to be fertile 40 years ago!
The names in the tables below are not exactly the same as in the article. Of the species shown in the original crossing chart, two, S. regina and S. discolor, have been merged with a third, S. speciosa, so they are not shown in my tables. S. claybergiana is now known as S. warmingii, S. warszewiczii is now known as S. incarnata (much to the relief of non-Slavic speakers everywhere), and S. verticillata is now known as S. douglasii.
[I must say I regret the loss of S. claybergiana. I never knew Dr. Clayberg, but I do know people who did. I never knew Herr Warming either, but Johannes Eugen Bülow Warming has other things named after him, such as a very nice Rhipsalis species (growing in my back yard), so we could have left one for Carl.]
In addition, two names, though matching those of currently recognized species, were most likely not those species. The S. canescens of the article was no doubt S. leucotricha, and the S. macropoda of the article was probably S. lineata, and these latter names are used in the table below.
In the first table, the species are arranged in alphabetical order. There are some clumps, but any underlying pattern is not obvious to the eye.
Now we rearrange the table, grouping the species which form fertile hybrids with one another.
The interesting thing about this table is that the species groupings are very close to those delineated by the molecular genetic studies of Perret et al. discussed elsewhere on this site.
It is easy to be condescending about these old hybridization experiments, given all the DNA data and analysis tools that are available these days. We need to keep in mind that Clayberg and his compatriots did all their own hybridization work, while almost none of us do either the DNA sequencing or sequence analysis for ourselves. Instead we rely on results published by others, on analytical computer programs written by others, or on data-analysis algorithms developed by others -- or all three!
Obviously, hybridization efforts did not stop with these results. Many more hybrids between species have been achieved since this data was gathered.
In particular, one suspects that diligent and tireless work would convert all the blank spaces in this table to s. Mauro Peixoto and others have obtained crosses between distant branches of the Sinningieae tribe, including some Paliavana x Sinningia hybrids. Everything suggests that