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 on 08 de fevereiro de 2021, 10:49 PM by tiwane