Argentenian and Chilean glabrous species (not including the hypericifolia-like plants)

I recently went through the glabrous species of Argentina and Chile and thought I'd document my findings here (partially so I can remember what I learned). The primary species were E. klotzchii and E. serpens, but I also investigated E. catamarcensis and E. serpillifolia. In addition, I've included some notes on the mysterious pistillate perianth that is common in E. klotzchii and E. serpens. The work is based on the monograph by Subils 1977 (Las Especies de Euphorbia de la República Argentina). Lastly, this is meant to exclude plants similar to E. hypericifolia (e.g., E. hypericifolia, E. hyssopifolia, and E. nutans). That group is far too complicated for a simple weekend survey to resolve.

The difference between E. klotzchii, E. serpens, and other entire and rounded leafed species of the region
Ultimately, the difference is in the stipules. In E. serpens, the stipules are fused into a triangular scale-like structure. In E. klotzchii, the stipules are distinct in one way or another. Additionally, E. klotzchii commonly produces leaf maculations while this never seems to happen in E. serpens. Lastly, E. klotzchii often assumes a more succulent and condensed appearance (easily noticed if you go through these observations).

There are two other similar species to be aware of: E. micromera (syn. E. ruizlealii). Euphorbia micromera is distinguished by it's small, rounded glands, total lack of glandular appendages, hairy stipules, and hairy lobes of the cyathium (there are plenty observations to reference on iNaturalist from North America, though the leaves are slightly differently shaped in South America as can be seen here). Euphorbia amandi has more rounded leaves like the other species mentioned here but produces serrated leaves.

Euphorbia klotzchii
Subils uses E. ovalifolia as used by Boissier. Without going into the taxonomic details (as the citations vary between this author's use and Euphorbia PBI), E. ovalifolia is considered a synonym of E. klotzchii. Under E. ovalifolia, Subils uses three varieties: E. ovalifolia var. ovalifolia, E. ovalifolia var. argentina, and E. ovalifolia var. schizosepala. None of these names are currently accepted and may just represent forms of the species. However, they all indicate some interesting aspects of the species' morphological variability. I've included a photo of each below in an attempt to show the differences (you may have to visit the pages and zoom in to tell the differences). Let's start with var. schizosepala. Note the little fringed appendage at the base of the fruit. This is considered a perianth (a perianth is a collective term for sepals and petals). In var. schizosepala, the perianth is long and easily differentiated from the fruit. In var. argentina, it becomes smaller and less noticable. In var. ovalifolia, it is completely absent.

E. ovalifolia var. schizosepala (source observation).

E. ovalifolia var. argentina (source observation).

E. ovalifolia var. ovalifolia (source observation).

Euphorbia serpens
Similar to E. klotchii, E. serpens produces a perianth in Chile and Argentina. Subils considers the plants that produce a perianth to be var. microphylla and the ones that don't to be E. serpens. Again, these varieties are not currently accepted, but useful for illustrating differences.

E. serpens var. microphylla (source observation).

E. serpens var. microphylla or somewhat intermediate (source observation).

E. serpens var. serpens (source observation).

Intriguingly, E. serpens has produced a large perianth in only one other location worldwide. That other location is in the Alps, Europe. There, the stipules aren't even fused and the variety goes by E. serpens var. fissistipula.

E. serpens var. fissistipula (source observation).

Euphorbia catamarcensis and E. serpillifolia, the narrow-leafed species

Seeds are most easily used to distinguishing E. catamarcensis and E. serpillifolia, though Subils also mentions that E. catamarcensis has a small and round pistillate perianth while E. serpillifolia doesn't. Additionally, Subils uses truncate leaf apices for E. serpillifolia, though I'm doubtful of the utility of this characteristic as the leaves of the plants I've seen aren't obviously truncate. One thing I did notice, though, is that the leaves of the plants that seem to align with E. serpillifolia have much more strongly asymmetric leaves and appear to have more cylindrical fruits (the later, an observation supported by Subils' description).

That said, any identification of E. serpillifolia should be treated as tentative. The species forms a morphologically variable complex in North America that is likely polyphyletic. Also, the lack of serrations on many leaves in the observations I'm calling E. serpillifolia in South America is troubling. It would not surprise me at all if the South American material ends up segregated into a new species or two. Ultimately, the situation requires further study. Below are some photos that I think represent both species.

E. catamarcensis (source observation).

E. serpillifolia (source observation).

Euphorbia amandi
E. amandi (syn. E. minuta Phil. as used by Subils) produces rounded serrated leaves. Currently, there don't seem to be any observations of E. amandi on iNaturalist, but if any show up that I can ID, they will be visible here. As for distinctions, the plant produces serrated leaves which should distinguish it from E. klotzchii, E. serpens, and E. micromera. To distinguish from E. serpillifolia and E. catamarcensis, the key provided by Subils is less helpful. The leaves of E. amandi should be rounder and less elongated, similar to E. klotzchii, E. serpens, and/or E. micromera.

Publicado el enero 15, 2023 03:17 MAÑANA por nathantaylor