Question for botanists: how do you describe the genus Euphorbia? This is not an identification question, just a matter of curiosity.
@nathantaylor is an expert on Euphorbias:
- Nathan is the top identifier of the genus, with over 200,000 Euphorbia IDs
- Nathan was mentioned in this Identifier Profile and this Observation of the Week
- Scroll to the end of the posts for more Euphorbia resources
Do you mean, what are the common characteristics of all Euphorbias that let botanists know that each is Euphorbia?
Not sure if this is what you are getting at, but personally I find it hard to describe the genus as currently circumscribed, because it contains such a huge diversity of forms worldwide as to have descriptive and predictive value more equivalent to most Tribes or Subfamilies. I find much more value in some of the narrower monophyletic groups that have been recognized within the genus. For example, I can always recognize a Chamaesyce when I see it in the field. But I can’t say the same for the whole genus Euphorbia.
they have highly specific inflorescences called cyathia, not found in any other plant, and unisexual flowers reduced to 1 stamen or 1 pistil,.
that said, there have been attempts to divide it into several genera (it would be easiest if it went to 4, Chamaesyce for mostly non-succulent mostly new-world plants (incl. things like poinsettia), Euphorbia and Rhizanthium for mostly succulent, cactus like old world plants, and Esula/Tithymalus for mostly old-world herbs). The problem is that Rhizanthium and Euphorbia are not eachothers closest relative , but are adapted to similar conditions and share both more and less drought adapted plants, and extreme xerophytes that evolved multiple times in both groups, so they are not morphologically easily definable. One solution would be to make the more or less well defined sections their own genera, resulting in maybe like 10-15 genera, or to keep it like it is, a genus united by its inflorescences, but not by it vegetative morphology. Most of the sections and subgenera are also quite old, I think. (while this is a solution, it is akin to putting all Apiaceae into Apium because their inflorescences are similar, and it makes a very large genus and obscures the diversity of Euphorbiaceae. But since genera are arbitrary it ultimately does not matter)