Medusoid Euphorbia species: synonomy

[chris_rex]

About a year ago I divided an old E flanagannii which had 10 to 15 heads. The species is said to be prone to this, when many others are not. Observing the plants today in their bewildering states of growth, some red, some green, some short armed, some long armed, some thin armed, some thick armed, about the only common feature is flower color and size. That is not surprising as these plants are clones. But yes, even species grown under the same conditions can look different. Imagine in habitat, under a variety of conditions, last century, botanists keen to describe species novae, ignoring the variability factor. A century later enter DNA to sort it all out !

In years gone by I had looked at Hawaiian species of the genus Pritchardia, and in the 1920s the monograph by a well known botanist Beccari had described about 5 new species collected from the Koolau mountains on Oahu. This century they have been reduced to synonomy.

Apparently, so it is with some South African Euphorbia. In 2012 Bruyns reduced the following in with E. Flanagannii. ernesti, gathergensis, franksiae, woodii, passa and discreta. In this paper he made specific mention of the variability of plants.

There was a massive problem caused by determining species then reviewing them based on the dried up old type specimens.

I can't say that I am surprised. I suspect there are really only about 5 or 6 distinct medusoid species in reality.

[Meangreen94z]

That’s very interesting. Do you have any photos showing the variability? Did all survive ?

[chris_rex]

Yes almost all survive. The lateral heads that form on E. flanaganii can be dipped in rooting hormone and under greenhouse conditions they seem to do well, some, better than others.

My current problem is telling E. flanaganii and E. gorgonis apart. Currently it is my belief that flanaganii produces lateral heads, but gorgonis does not.

Geoff Stein has reported:

" Euphorbia gorgonis is a moderately common species that I have difficulty distinguishing from Euphorbia flanaganii. The overall shape, size, arm anatomy and flower color is nearly identical, though Euphorbia gorgonis seems to be a less aggressive grower with much shorter arms..."

Does anyone have another differentiating characteristic?

[chris_rex]

Additional information I have is that E. gorgonis is now recognised as E. procumbens ( as is pugniformis) in the Kew checklist.
In the molecular phylogeny in Taxon 62 (6) December 2013, E. gorgonis is therefore E. procumbens and is sister to flanaganii ( Pierson, Bruyns et al ) so must be close in characteristics.
No wonder Geoff Stein had problems splitting them!
According to Kew, E. esculenta is still recognised species , as is inermis.