A Euphorbia Observation in Brazil Provides Tantalizing Natural History Clues - Observation of the Week, 2/8/21

Our Observation of the Week is this likely Euphorbia duckei plant, seen in Brazil by @nelson_wisnik.

While he always enjoyed being out in nature, Nelson Wisnik says “I only started paying more attention to fauna and flora when I became a professor of physics in forestry and agricultural engineering courses, showing how physical conditions shape beings, how the energy flow governs the interactions between them, from the point of view of physics.”

Now retired, he spends much of his time trying to observe, record, and share biodiversity. After living on a boat in the central Amazon region from 2002-2008, he spends several months every year exploring the area. He’s also volunteered as an environmental educator in Brazil as well. And of course, that’s where he came across these peculiar plants.

“In the region of the mouth of the Tapajós River, the level of the rivers presents an annual variation of approximately 6.5 m (21 feet) between flood and ebb,” explains Nelson.

The beaches appear on the banks of the rivers and vast areas of lowland are drained, allowing the growth of many species of plants, which, in turn, attract a wide variety of fauna, including migratory species. In this scenario, on two occasions I observed, among other species of the same genus, the Euphorbia duckei. Not being a botanist or biologist, I didn't immediately realize the value of these observations, but [only] later on, during the discussion about their identification.

That discussion included @trh_blue and @nathantaylor, who is iNat’s top Euphorbia identifier. While Nathan says “the only way to be absolutely sure is to see a cyathium on the plant,

E. duckei is the only species known from Brazil that gets that woody and shrubby and has straight branches like those in the observation. What's more, the type locality is along the Tapajós River (the observation was found where the Tapajós River meets the Amazon River.) While geography alone doesn't rule out other species growing in the area and morphology isn't enough to rule out the possibility of an undescribed species or some other new occurrence, together they give pretty good evidence for the identity of the species.

Nathan is quite sure that, aside from the type specimen, these are the only records of E. duckei online and tells me they provide a lot of interesting life history information that wasn’t previously available. “To give a sense of how little is given about the species,” says Nathan,

I'll quote the describer of the plant Léon Croizat in 1943: "The characters of this plant are outstanding, and that it represents a new species seems to be obvious. The material, however, is hardly satisfactory for a generalized description, because it shows a stage in which the new growth is barely beginning, but the old branchlets have already lost their leaves." The observations [Nelson actually observed this species in 2018 as well - Tony] provided show most of what the type specimen lacks. It also gives a more accurate scale of the plant that a specimen simply can't provide. But more interesting to me than the above, it shows the habitat of the species. The observations show that the plant can clearly survive with their roots under water, a condition that would kill any perennial sandmat. Given the comments of the observer that the plants are underwater much of the year, this could represent the first example of an emergent aquatic sandmat.

The thing that I find most fun about this is that Léon Croizat named the species Euphorbia duckei after Adolpho Ducke, likely having no inclination about the conditions under which the plants grew. The humor in this name may already be apparent to you, but I can't help but wonder if any future student will look at the plant and the habitat and use the associations with "duckies" as a way to help them remember the name.

Nelson (above) has contributed over 12,000 observations and nearly 10,000 IDs to iNaturalist so far, and tells me

In my opinion, iNaturalist is the most complete biodiversity data platform that best adapts to my objective, that is, to give visibility to my observations, so that the information contained therein is accessible for scientific studies and educational activities.

Through the direct collaboration of the participants, to whom I am very grateful, the use of iNaturalist taught me not only about the species I had observed, but also how to proceed and be more attentive in observing biodiversity.

- Another one of Nelson’s observations was chosen as Observation of the Day a few years ago. Take a look and then read his journal post about it.

The genus Euphorbia contains around 2,000 species, here are the most-faved observations of plants in this genus on iNat.

- Nathan has posted a ton of resources about euphorbias and other taxa, here’s a hub of links to some of his work.

- Nathan talked euphorbias and iNat on the In Defense of Plants podcast.

Posted by tiwane tiwane, February 08, 2021 22:49


Congrats Nelson, and thanks for all your contributions to iNat! Thanks also to Nathan, of course.
And I just can't get over duckei, it's too perfect.

Posted by trh_blue 8 months ago (Flag)

Oh, and if anyone wants more beautiful photos/observations of Euphorbia, sandmats especially, hit me up. I've got a huge supply of links.

Posted by trh_blue 8 months ago (Flag)

So happy to see this get featured! It's such an interesting little plant.

Posted by nathantaylor 8 months ago (Flag)

Well done Nelson -- very interesting indeed!

Posted by susanhewitt 8 months ago (Flag)

Awesome observation! Thanks for your contributions.

Posted by bethd 8 months ago (Flag)


Posted by leptonia 8 months ago (Flag)

Wow, great job @nelson_wisnik, @leaf1234, @trh_blue, and @nathantaylor with that progressively finer string of identifications!

Posted by carrieseltzer 8 months ago (Flag)

Great job @nelson_wisnik

Posted by aravinth6 8 months ago (Flag)

Great observation Thank you

Posted by leaf0605 8 months ago (Flag)

Be sure to watch for infection by downy mildew! More likely than not it'd be an undescribed species of Peronospora.

Posted by daviswj 7 months ago (Flag)

@daviswj Interesting! Mildew seems to be pretty rare in the section and in Euphorbia in general (here are the observations I've aggregated of fungi on Euphorbia: https://www.inaturalist.org/observations?place_id=any&project_id=organisms-associated-with-euphorbia&subview=grid&taxon_id=47170&verifiable=any). Do you know if there are in specialists in Euphorbia, or better yet, in sect. Anisophyllum?

Posted by nathantaylor 7 months ago (Flag)

I think it's also important to highlight that the first observation of Euphorbia duckei was hidden from view for two whole years since it was labeled under the kingdom Plantae. It makes you wonder how many more diamonds in the rough like this you'd be able to find if you searched around through all the observations labeled in the higher taxons. If @leaf1234 hadn't labeled the observation under Euphorbiaceae, this probably wouldn't have been found for a while. Thanks to all those who go through Plantae observations and refine the IDs!

Also, I searched around in most of Brazil's Plantae observations and while I was able to find two previously unlabeled Euphorbia, none were E. duckei (I really wanted to see if I could find one with cyanthium!). I guess there's still the possibility.

Posted by rynaturalist 7 months ago (Flag)

Yeah, it's cool to find interesting specimens in the coarsely IDd stuff! It's why I do a mix of coarse and specialized ID work. I take a look at everything IDd to Euphorbiaceae or Euphorbia, and a number of species. You can always tag me too. I don't know nearly as much as Nathan but I have way more spare time :)

Posted by trh_blue 7 months ago (Flag)

Too cool! This is one of the many reasons I love iNaturalist - the keen amateur can post something that can be picked up by someone who knows much more, and everyone involved gains knowledge! It’s magical.

Posted by lisa_bennett 7 months ago (Flag)

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